Behavioral Health: Group Psychotherapy

Number: 1100

Table Of Contents

Policy
Applicable CPT / HCPCS / ICD-10 Codes
Background
References

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Policy

Scope of Policy

This Clinical Policy Bulletin addresses behavioral health group psychotherapy.

1. Medical Necessity

   Subject to applicable benefit plan terms and limitations, Aetna considers behavioral health group psychotherapy medically necessary when all of the following criteria are met (see Appendix for Patient Selection and Contraindications):

   1. Services are ordered by a physician or independently licensed behavioral health professional (BHP) (i.e., psychiatrist, clinical psychologist, psychiatric-mental health nurse practitioner [PMHNP], physician associate [PA], social worker [LCSW], marriage and family therapist [LMFT] or professional counselor [LPC] licensed to practice without supervision in their State); and 
   2. Member has a documented DSM‑5‑TR diagnosis of a behavioral health disorder that is appropriate for group‑based intervention (e.g., depressive disorders, anxiety disorders, trauma‑related disorders, substance use disorders, personality disorders that respond to skills groups); and 
   3. The condition results in clinically significant functional impairment in social, occupational, academic, or interpersonal domains; and
   4. The diagnosis and level of need are established through a documented treatment plan performed by a physician or licensed BHP within the past 90 days; and
   5. Member is able to participate safely in a structured therapeutic group without posing risk of harm to self or others; and
   6. Member's cognitive capacity is sufficient to engage in verbal therapeutic processes, attend to group discussions, and follow group norms; and
   7. Group therapy meets all of the following program requirements:
      
      
      1. Therapy is conducted by a clinician licensed to deliver psychotherapy within scope of practice (e.g., clinical psychologist, LCSW, LPC, LMFT, PMHNP, PA, MD/DO); and
      2. Curriculum is based on evidence-based practices tailored to the specific needs and diagnoses of the participants (e.g., substance use disorders, trauma, anxiety); and
      3. Group size does not exceed 12 participants to ensure effective interaction and individual attention; and

   8. Documentation will also include the following:

      1. Expected frequency and number of sessions; and
      2. Date, duration, and type of service (e.g., cognitive, dialectical behavior, interpersonal process, psychoeducational, skills development, specialized clinical group); and
      3. Therapeutic goals and interventions; and
      4. Member participation and progress toward treatment plan objectives; and 
      5. Signature and credentials of the provider.

2. Policy Limitations and Exclusions 

   Coverage may vary according to the member's benefit plan. Please check benefit plan descriptions for details.

3. Related Policies 

   • CPB 0132 - Biofeedback
   • CPB 0214 - Cognitive Rehabilitation
   • CPB 0237 - Chronic Pain Rehabilitation Programs
   • CPB 0256 - Sensory and Auditory Integration Therapy
   • CPB 0370 - Phototherapy for Psychiatric Disorders
   • CPB 0426 - Attention Deficit/Hyperactivity Disorder
   • CPB 0480 - Tourette's Syndrome
   • CPB 0511 - Eating Disorders
   • CPB 0648 - Autism Spectrum Disorders
   • CPB 0730 - Home Behavioral Healthcare Services
   • CPB 0999 - Prescription Digital Therapeutics

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Table:

CPT Codes / HCPCS Codes / ICD-10 Codes

Code	Code Description
CPT codes covered if selection criteria are met:
90849	Multiple-family group psychotherapy
90853	Group psychotherapy (other than of a multiple-family group)
HCPCS codes covered if selection criteria are met:
C7903	Group psychotherapy service for diagnosis, evaluation, or treatment of a mental health or substance use disorder provided remotely by hospital staff who are licensed to provide mental health services under applicable state law(s), when the patient is in their home, and there is no associated professional service
ICD-10 codes covered if selection criteria are met:
F06.4	Anxiety disorder due to known physiological condition
F07.0-F07.9	Personality and behavioral disorders due to known physiological condition
F10.10-F19.99	Mental and behavioral disorders due to psychoactive substance use
F21	Schizotypal disorder
F32.0-F32.A	Depressive episode
F33.0-F33.9	Major depressive disorder, recurrent
F34.0	Cyclothymic disorder
F34.1	Dysthymic disorder
F40.00-F40.9	Phobic anxiety disorders
F41.0-F41.9	Other anxiety disorders
F43.10-F43.12	Post-traumatic stress disorder (PTSD)
F43.20-F43.29	Adjustment disorder
F43.81-F43.89	Other reactions to severe stress
F44.81	Dissociative identity disorder
F45.21	Hypochondriasis
F51.5	Nightmare disorder
F60.0-F60.9	Specific personality disorders
F68.10-F68.A	Other disorders of adult personality and behavior
F69	Unspecified disorder of adult personality and behavior
F93.0	Separation anxiety disorder of childhood
F94.0-F94.9	Disorders of social functioning with onset specific to childhood and adolescence
ICD codes that are temporarily inappropriate for group treatment section:
F02.C11-F02.C18	Dementia in other diseases classified elsewhere, severe, with behavioral disturbance
F03.C11-F03.C18	Unspecified dementia, severe, with behavioral disturbance
F06.0	Psychotic disorder with hallucinations due to known physiological condition
F71	Moderate intellectual disabilities
F72	Severe intellectual disabilities
F80.1	Expressive language disorder
F80.2	Mixed receptive-expressive language disorder
R47.01-R47.02	Dysphasia and aphasia

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Background

Group therapy is a form of psychotherapy that involves a small group of individuals who meet regularly to discuss their thoughts, feelings, and experiences under the guidance of a trained therapist. This therapeutic approach is designed to create a supportive, cohesive environment where participants can share their challenges and gain insights from one another (Burlingame et al., 2011; Burlingame et al., 2018; Corey, 2016). The group dynamic fosters a sense of community and belonging, which can be particularly beneficial for individuals dealing with similar issues, such as anxiety, depression, or trauma. According to the American Group Psychotherapy Association (Bernard et al., 2008), group therapy conducted by an appropriately trained provider can enhance self-awareness and interpersonal skills while providing a platform for individuals to practice new behaviors in a safe setting.

One of the key benefits of group therapy is the opportunity for participants to learn from each other's experiences. Members can offer support, feedback, and different perspectives, which can lead to greater understanding and personal growth. The therapist facilitates discussions, encourages participation, and helps the group navigate any conflicts that may arise (Bernard et al., 2008; Burlingame et al., 2011; Burlingame et al., 2018; McCarthy et al., 2021; Corey, 2016). Research has shown that group therapy can be as effective as individual therapy for many mental health conditions, and it often provides a cost-effective alternative (Yalom & Leszcz, 2020). The shared experience of group members can also reduce feelings of isolation, as individuals realize they are not alone in their struggles (Burlingame et al., 2011; Burlingame et al., 2018; McCarthy et al., 2021).

Group therapy can take various forms, including support groups, skills training groups, and process-oriented groups, each tailored to meet the specific needs of participants. Therapist-led support groups focus on providing emotional support, while skills training groups teach coping strategies and techniques. Process-oriented groups delve into interpersonal dynamics and personal growth (Yalom & Leszcz, 2020; Corey, 2016). Regardless of the format, the therapeutic alliance formed within the group is crucial for its success (Burlingame et al., 2011; Burlingame et al., 2018). As noted by the American Group Psychotherapy Association, the collaborative nature of group therapy can lead to improved outcomes for individuals seeking to enhance their mental health and well-being (Bernard et al., 2008).

Behavioral health group therapy is a structured, evidence-based, and efficacious form of psychotherapy led by a licensed psychiatric provider or therapist in which a small group of patients meets regularly to address shared psychological, emotional, or behavioral concerns. Group therapy can function as an independent outpatient treatment or may exist as part of a treatment plan in an intensive outpatient program, a partial hospitalization program, or in residential/inpatient care. As such, group therapy goals, content, and structure will vary based on the level of care, patient population, and the problems being addressed. Sessions are designed to promote insight, coping skills, interpersonal growth, and symptom reduction through interaction with peers and guidance from a licensed clinician (Yalom & Leszcz, 2020; Bernard et al., 2008; Burlingame et al., 2011; Burlingame et al., 2018; McCarthy et al., 2021; Corey, 2016).

Key therapeutic factors include universality, cohesion, interpersonal learning, altruism, catharsis, instillation of hope, and skill development. The therapeutic process draws on both the therapist’s expertise and the healing dynamics of peer relationships within the group for members suffering from mental health and/or substance use disorders. Group therapy differs from peer-led support groups, educational classes, or social activities, which may offer benefits but do not involve licensed therapeutic intervention (Yalom & Leszcz, 2020; Bernard et al., 2008; Burlingame et al., 2011; Burlingame et al., 2018; McCarthy et al., 2021; Corey, 2016).

Specifically, group psychotherapy is clearly distinguished in the professional literature from informal support groups, peer-led interventions, and psychoeducational or self-help gatherings. Authoritative texts emphasize that group psychotherapy is a regulated mental health treatment designed to address psychological distress, interpersonal functioning, and psychiatric symptoms through structured, theory-driven clinical processes (Yalom & Leszcz, 2020; Bernard et al., 2008; Corey, 2016). It is therefore not defined by group discussion alone, but by the intentional application of therapeutic interventions, assessment, and ongoing clinical judgment. Practice guidelines from the American Group Psychotherapy Association (AGPA) and the Association for Specialists in Group Work (ASGW) explicitly differentiate psychotherapy groups from support or task groups, underscoring that psychotherapy groups require advanced clinical training and ethical accountability (Bernard et al., 2008; McCarthy et al., 2021).

Many peer-reviewed resources define group psychotherapy by clarifying what falls outside its ethical and clinical boundaries. Group therapy is not an unstructured forum for emotional expression without therapeutic intent, nor is it a setting in which facilitators may exceed their training or provide interventions unsupported by evidence (Yalom & Leszcz, 2020; McCarthy et al., 2021; Corey, 2016). Ethical frameworks emphasize that clinicians must practice within the limits of their education, training, and experience and must obtain additional supervision or refer clients when group members’ needs exceed their competence (McCarthy et al., 2021; Barnett & Johnson, 2015). Failure to adhere to these principles undermines treatment effectiveness and increases the likelihood of ethical violations and psychological harm (Barnett & Johnson, 2015).

For clarity, group therapy must be led or supervised by a licensed specialist in group therapy. Additionally, many activities do not qualify as group therapy and, as such, should not be billed under the group therapy code.

• Support groups without a trained therapist

  Peer-led or self-help groups (e.g., Alcoholics Anonymous, grief support circles) can be helpful but do not involve clinical assessment, diagnosis, or psychotherapeutic interventions.

• Educational or psychoeducational classes only

  Examples include workshops, lectures, or skill classes (e.g., parenting courses, stress management seminars) that provide information but do not actively process emotions, relationships, or personal history in a therapeutic manner.

• Activity-based groups without therapeutic processing

  This includes recreational groups (e.g., art, music, yoga or exercise classes) that focus on the activity rather than using it as part of a structured psychotherapeutic process.

• Meetings for coordination or planning

  This includes case conferences, work meetings, treatment team huddles, or other administrative group meetings.

• Social gatherings

  This includes any group meeting where the primary purpose is companionship, entertainment, or networking, without a guided therapeutic goal.

Group Therapy Efficacy

Group therapy has been shown to be helpful in managing a wide range of psychiatric and medical conditions. The key benefit of group therapy lies in providing patients with a supportive, structured environment where they can share experiences, gain insight, and receive feedback. While not an exhaustive list, there is a significant number of peer-reviewed articles that support the effectiveness of group therapy in managing a multitude of psychiatric and medical conditions.

As previously noted, group therapy is a widely used psychotherapeutic modality in which one or more trained clinicians facilitate treatment with multiple participants simultaneously (Yalom & Leszcz, 2020; McCarthy et al., 2021; Corey, 2016; Bernard et al., 2008). Its theoretical foundations draw from interpersonal, psychodynamic, cognitive-behavioral, and humanistic traditions, emphasizing the role of social interaction in psychological change (Burlingame et al., 2018). Rather than focusing exclusively on intrapsychic processes, group therapy conceptualizes psychological distress as embedded within relational and social contexts, allowing members to learn through shared experience, feedback, modeling, and mutual support (Corey, 2016; Yalom & Leszcz, 2020).

Several core therapeutic factors are considered central to the effectiveness of group therapy. These include universality, instillation of hope, imparting of information, altruism, development of socializing techniques, imitative behavior, interpersonal learning, group cohesiveness, and catharsis (Yalom & Leszcz, 2020). Among these, group cohesiveness has been consistently identified as one of the strongest predictors of positive treatment outcomes and is often conceptualized as analogous to the therapeutic alliance in individual psychotherapy (Burlingame et al., 2013; Burlingame et al., 2018). The interactive nature of the group provides opportunities for corrective emotional experiences, in which maladaptive interpersonal patterns can be identified and modified in real time (Corey, 2016; Bernard et al., 2008; Yalom & Leszcz, 2020).

A robust body of empirical research supports the efficacy of group therapy across a wide range of psychiatric diagnoses. Meta-analytic evidence suggests that group psychotherapy is effective for major depressive disorder, generalized anxiety disorder, social anxiety disorder, post-traumatic stress disorder, substance use disorders, and schizophrenia, with effect sizes comparable to those observed in individual therapy (Burlingame et al., 2021; Cuijpers et al., 2016). Group cognitive-behavioral therapy has demonstrated efficacy for mood and anxiety disorders, producing significant reductions in symptom severity and improvements in functioning (Cuijpers et al., 2016).

Group therapy has demonstrated effectiveness for individuals with depressive disorders, especially major depressive disorder and persistent depressive disorder. Group-based cognitive-behavioral therapy and interpersonal process groups have been shown to reduce depressive symptoms by addressing maladaptive cognitions, interpersonal deficits, and social withdrawal common in depression (McDermut et al., 2001; Cuijpers et al., 2016). The group format offers opportunities for behavioral activation through social engagement and provides corrective feedback that challenges depressive cognitive distortions, such as perceived burdensomeness and hopelessness (Yalom & Leszcz, 2020). Universality and instillation of hope are especially salient for depressed individuals, as observing symptom improvement in peers can counteract feelings of isolation and despair (Burlingame et al., 2011; Burlingame et al., 2018; Burlingame et al., 2021). Additionally, Cuijpers et al. (2016) and others demonstrated the effectiveness of group therapy in supporting depression in the context of chronic medical conditions, including cancer, insomnia, chronic pain, multiple sclerosis, hemodialysis patients, and cardiac patients.

Anxiety disorders are also highly responsive to group therapy, particularly social anxiety disorder, generalized anxiety disorder, and panic disorder (Cuijpers et al., 2016). Group cognitive-behavioral therapy allows for in vivo exposure to feared social situations, cognitive restructuring, and skills rehearsal within a supportive environment (Heimberg & Becker, 2002). For individuals with social anxiety, the group itself functions as both the treatment context and the exposure stimulus, facilitating habituation and improved social competence (Heimberg & Becker, 2002; Cuijpers et al., 2016). Similarly, trauma-focused group interventions for post-traumatic stress disorder have been shown to reduce avoidance and hyperarousal while promoting emotional processing and peer support (Sloan et al., 2013).

Group therapy is frequently used in the treatment of substance use disorders, where peer accountability and shared recovery goals play a central role in behavior change. Evidence supports the effectiveness of relapse prevention groups, motivational enhancement groups, and 12-step-oriented group interventions in reducing substance use and improving treatment retention (Weiss et al., 2005; Yalom & Leszcz, 2020). The altruistic aspects of group therapy—such as offering support to others—are particularly therapeutic for individuals in recovery and may enhance self-efficacy and long-term abstinence (Burlingame et al., 2018; Burlingame et al., 2021). Group therapy is also a core component of treatment for severe mental illnesses, including schizophrenia and bipolar disorder, where psychoeducational and skills-based groups have been shown to improve illness insight, medication adherence, and social functioning (Dixon et al., 2010).

Further, in a recent series of 11 meta-analyses encompassing over 329 studies and 370 comparisons of group versus individual therapy, group therapy was found to be effective for depression and bipolar disorders, schizophrenia, anxiety disorders, social anxiety disorder, panic disorders, obsessive-compulsive disorder, post-traumatic stress disorder, eating disorders, borderline personality disorder, substance use disorders, and chronic pain (Rosendahl et al., 2021). Findings indicate that group therapy offers comparable clinical outcomes while providing greater cost-effectiveness and increased access to care, particularly in public and community mental health settings (Burlingame et al., 2018; Corey, 2016). These advantages make group therapy especially valuable in addressing treatment demand, long waitlists, and workforce limitations. Furthermore, group formats may enhance treatment retention by fostering accountability and social reinforcement among members (Yalom & Leszcz, 2020).

Cultural and contextual factors play an important role in group therapy processes and outcomes. Culturally responsive group therapy can promote empowerment, collective healing, and validation of shared sociocultural experiences, particularly among marginalized populations (Craig et al., 2021; Rafieifar & Macgowan, 2021). When facilitated with cultural humility and awareness, group therapy can strengthen identity development and resilience while addressing systemic stressors that contribute to mental health disparities (Corey, 2016; Craig et al., 2021; Rafieifar & Macgowan, 2021).

Overall, group therapy has a significant positive impact on mental health outcomes by addressing both symptom reduction and broader psychosocial functioning. Across psychiatric and medical populations, it enhances emotional regulation, interpersonal effectiveness, social connectedness, and long-term coping skills (Burlingame et al., 2021; Yalom & Leszcz, 2020). Its strong empirical support, adaptability across diagnoses, and efficiency reinforce group therapy’s role as a core evidence-based intervention within modern mental health care systems.

Provider Qualifications

The effectiveness and ethical delivery of group therapy depend heavily on the training and licensure of the group facilitator. Effective group therapy is conducted by licensed mental health professionals, including psychologists, psychiatrists, licensed clinical social workers, licensed professional counselors, licensed mental health counselors, marriage and family therapists, licensed nurses and advanced practitioners, and other licensed or qualified mental health providers, depending on jurisdictional scope of practice (Bernard et al., 2008). These providers are trained to manage group dynamics, screen participants appropriately, address risk factors such as suicidality, and maintain ethical standards related to confidentiality and dual relationships within the group context (Corey, 2016; Bernard et al., 2008; APA, 2017).

Ethical and professional standards consistently state that individuals without appropriate licensure or legal authority should not conduct group psychotherapy intended to treat mental health disorders. Group psychotherapy is considered the practice of psychotherapy and is therefore subject to state licensing laws and professional regulation (McCarthy et al., 2021; Barnett & Johnson, 2015; Bernard et al., 2008). Unlicensed individuals practicing independently—including lay facilitators, coaches, or wellness providers—are not authorized to diagnose or treat mental disorders and may place clients at risk due to inadequate training in assessment, crisis intervention, and ethical decision-making (Yalom & Leszcz, 2020; Barnett & Johnson, 2015). Ethical codes emphasize that practicing outside one’s scope of competence constitutes a violation of professional standards and may result in client harm (APA, 2017).

The literature further clarifies that students and trainees may only conduct group psychotherapy under formal, ongoing supervision by a licensed mental health professional. Supervision is considered essential for client safety, professional development, and ethical accountability, particularly given the complexity of managing multiple clients simultaneously in group settings (Falender & Shafranske, 2004; Bernard et al., 2008). Students who conduct psychotherapy without supervision are not considered competent to independently screen participants, manage group dynamics, or respond to clinical emergencies such as suicidality, aggression, or boundary violations (Corey, 2016). Ethical standards uniformly state that supervisors retain responsibility for clinical services delivered by trainees and must ensure that supervision is sufficient in intensity and scope (APA, 2017; Falender & Shafranske, 2004).

Psychiatrists may additionally provide group therapy in conjunction with medication management, particularly in hospital or intensive outpatient settings, while psychologists often lead specialized process or evidence-based groups that require advanced training in assessment and psychotherapy research (Yalom & Leszcz, 2020). Social workers and counselors frequently facilitate groups in community mental health, substance use treatment, and medical settings, where a systems-based and recovery-oriented approach is emphasized (Weiss et al., 2005). Regardless of discipline, best-practice guidelines emphasize that clinicians conducting group therapy should have formal education in group theory, supervised group facilitation experience, and ongoing consultation or continuing education specific to group work (Bernard et al., 2008).

Overall, aligning specific diagnoses with empirically supported group therapy models and appropriately trained licensed providers enhances both treatment outcomes and patient safety. Burlingame and Barlow (1996) noted that professional and nonprofessional (i.e., unlicensed) therapists yielded similar immediate outcomes in short-term group therapy, but professionals fostered deeper insight and catharsis, leading to better six-month follow-up results, suggesting they help create longer-lasting change by focusing on processes like insight more effectively than "natural helpers." When facilitated by qualified clinicians, group therapy serves as a versatile, evidence-based intervention that addresses diagnostic symptoms while simultaneously fostering interpersonal growth, social connection, and long-term recovery across a wide range of mental health conditions (Burlingame et al., 2018; Burlingame et al., 2021; Yalom & Leszcz, 2020).

Additionally, evidence-based practice guidelines and ethical codes consistently define group psychotherapy as a specialized clinical intervention that must be conducted by licensed professionals or supervised trainees with appropriate training in group work. It is not synonymous with peer support, wellness programming, or informal group facilitation, nor is it ethically delivered by individuals without formal clinical preparation and accountability (Bernard et al., 2008; APA, 2017; Yalom & Leszcz, 2020). These distinctions serve to protect clients, uphold professional integrity, and reinforce group psychotherapy’s status as a legitimate and regulated form of mental health treatment.

In summary, group therapy may only be provided by:

• Licensed behavioral health professionals (e.g., psychiatrists, psychologists, licensed clinical social workers, licensed professional counselors, licensed marriage and family therapists, licensed chemical dependency counselors, psychiatric nurse practitioners, physician assistants/associates with psychiatric training).
• Unlicensed or provisionally licensed clinicians only under direct supervision of a licensed provider (listed above), in compliance with state and federal regulations.
  
  
  • Direct supervision means that a licensed and credentialed behavioral health professional is responsible for overseeing and guiding the clinical work of the unlicensed/provisionally licensed clinician and is physically present on-site and immediately accessible to the clinician.
  • The licensed supervisor has the ultimate responsibility for the quality of care, all clinical decision-making, co-signing clinical documentation, and conduct of the group therapy session.

Group Size

Group psychotherapy is a form of psychological treatment in which several individuals meet with one or more trained clinicians to work on shared or individual concerns. Beyond simple cost-efficiency, group therapy offers unique therapeutic mechanisms, including opportunities for social learning, normalization of experiences, interpersonal feedback, and the development of cohesion and mutual support (Kivlighan et al., 2020). These relational processes are thought to contribute substantially to outcomes, distinguishing group therapy from individual formats and making the structure and organization of the group—such as composition, cohesion, and size—central design considerations (Kivlighan et al., 2020).

A growing body of research has asked whether group size itself influences therapeutic effectiveness. Findings are mixed but informative. Some studies suggest that very large groups may dilute therapeutic exposure, reduce individual participation time, and challenge the formation of cohesive bonds, leading to smaller symptom reductions compared with moderately sized groups (Wilson et al., 2018; Ezhumalai et al., 2018). A recent systematic review similarly reported that group size showed significant associations with outcomes or cohesion in several studies, often trending toward better results in smaller or moderately sized groups, while also noting variability across populations and modalities (Twomey & Dowling, 2025). At the same time, other analyses have found that group size does not consistently moderate outcomes once other design and process variables are accounted for, highlighting the complexity of isolating its effect (Kivlighan et al., 2020).

From a clinical planning perspective, these data have informed pragmatic recommendations rather than rigid rules. Practice-oriented reviews and policy analyses frequently suggest that groups of approximately 5 to 9 members strike a balance between sufficient interpersonal diversity and adequate engagement time per participant (Dueweke, 2022). Groups that are too small may lack varied perspectives and momentum, whereas groups exceeding roughly 10 to 12 members may place heavier demands on facilitators and risk fragmentation or reduced cohesion (Dueweke, 2022; Twomey & Dowling, 2025; Ezhumalai et al., 2018). Ultimately, the literature converges on the idea that optimal group size is context-dependent: it interacts with treatment model (e.g., skills-based vs. process-oriented), facilitator expertise, and the clinical characteristics of participants.

As previously noted, group therapy is an effective modality supported by robust interpersonal mechanisms, and group size appears to be one meaningful—though not singular—determinant of its efficacy. Evidence suggests that moderately sized groups often function best (Dueweke, 2022; Twomey & Dowling, 2025; Ezhumalai et al., 2018), but the strongest conclusions emphasize thoughtful tailoring rather than one “correct” number. Clinicians are therefore encouraged to consider group size as a modifiable structural feature, evaluated alongside cohesion, composition, and facilitator practices, when designing or refining group-based interventions. However, literature does appear to point to a loss of efficacy in group therapy at patient numbers exceeding 12.

A substantial body of literature underscores that structural variables in group psychotherapy—particularly group size—must be considered in concert with relational processes such as cohesion, group composition, and facilitator practices. Cohesion, typically defined as the sense of belonging, trust, and commitment among group members, has been identified as a central mechanism of change in group-based interventions (Burlingame et al., 2018). Meta-analytic findings demonstrate a consistent, moderate association between cohesion and clinical improvement across diagnostic categories and treatment models, suggesting that groups characterized by high cohesion provide a context in which disclosure, mutual support, and collaborative engagement are more likely to occur (Burlingame et al., 2018). Importantly, several reviews note that structural characteristics such as group size may indirectly influence outcomes through their effects on cohesion, highlighting an interaction rather than a simple additive effect (Kivlighan et al., 2020).

Group size also interfaces with member engagement, composition, and attendance, both of which are reliable predictors of treatment response. Larger groups may inadvertently reduce opportunities for individual participation, limit direct contact with facilitators, and increase the likelihood of side conversations or subgroup formation (Bernard et al., 2008; Corey, 2016). Empirical studies have shown that lower cohesion and weaker alliances are associated with decreased session attendance and diminished therapeutic involvement, which in turn mediate poorer outcomes (Burlingame et al., 2018; Burlingame et al., 2021). These findings suggest that clinicians should conceptualize group size not merely as a logistical parameter but as a factor that shapes the quality and distribution of interactional opportunities within a diverse group.

Facilitator competence plays a critical moderating role across these dynamics. Practice guidelines emphasize early clarification of norms, explicit attention to safety and confidentiality, and intentional cultivation of member-to-member interactions as core strategies for establishing a therapeutic group climate (Bernard et al., 2008; McCarthy et al., 2021). Skilled facilitators actively monitor emerging relational patterns, intervene to promote equitable participation, and model constructive interpersonal processes. These practices can buffer some of the challenges posed by larger groups and enhance the therapeutic potency of moderately sized groups by channeling interaction toward shared goals (McCarthy et al., 2021).

In the context of group therapy for substance abuse treatment, the Substance Abuse and Mental Health Services Administration (SAMHSA, 2005) identifies five key therapy models: Psychoeducational groups, Skills Development groups, Cognitive-Behavioral/Problem Solving groups, Support groups, and Interpersonal Process groups. Psychoeducational groups are designed to help clients recognize, avoid, and ultimately master the internal states and external circumstances associated with substance abuse, often integrating coping skills such as anger management and the use of “I” statements. While these groups are vital and beneficial, they are not sufficient on their own; they facilitate clients' progression from precontemplation to a commitment to treatment, thereby setting the stage for other therapeutic modalities. Typically structured and often guided by a manual, psychoeducational groups promote self-reflection, problem-solving, and self-esteem enhancement in a quiet and private environment. Skills Development groups concentrate on teaching specific skills tailored to individual client needs, ideally consisting of 8 to 10 participants to allow for effective practice. Cognitive-Behavioral groups are particularly beneficial in early recovery, focusing on social support and coping strategies through a structured 24-session program that incorporates educational tools and addresses both substance use and PTSD symptoms. Support groups help members manage their thoughts and emotions while tackling practical issues related to maintaining abstinence. Finally, Interpersonal Process groups utilize psychodynamic principles to encourage change and healing by examining the unconscious conflicts that shape behavior.

Ezhumalai et al. (2018) discuss the practical considerations for conducting group interventions for individuals with substance use disorders, including the skills required by group therapists and the benefits of participating in such interventions. The research conducted at NIMHANS on group interventions for substance use disorders highlights the assessment of group processes, dynamics, and outcomes. Group therapy is recognized as a promising psychosocial treatment modality employed in clinical settings by qualified mental health professionals, including psychiatrists, clinical psychologists, psychiatric nurses, social workers, and occupational therapists. The group therapist plays an active role in helping members understand both their individual and interpersonal challenges, with discussions centered on current issues affecting themselves and others. The goals of group therapy include reducing negative symptoms, enhancing motivation, and improving social functioning, adjustment, and interpersonal relationship skills. Key principles for effective group interventions include selecting individuals based on the similarity of their problems, maintaining an optimal group size of 8 to 12 members, ensuring appropriate seating arrangements, and determining the frequency of sessions, which can range from once a week to several times a day, depending on the needs of the members. Additionally, group therapy sessions may last up to 90 minutes and can extend for a maximum of 25 sessions or six months, with participants ideally falling within a similar age range of 25 to 55 years to minimize age disparity.

The American Group Psychotherapy Association (AGPA) has established Practice Guidelines for Group Psychotherapy, outlining their application in clinical practice and training environments. The AGPA acknowledge that starting group therapy can be a highly anxiety-inducing experience for clients, and despite thorough preparation, uncertainties often persist. Clients may struggle to fully absorb verbal information due to anxiety, highlighting the importance of providing written materials. It is essential for clients to have a clear understanding of the group's structure, including details such as the meeting location, schedule, session duration (typically one and a half to two hours), group length if time-limited, and the number of participants (generally 7 to 10). In clinical settings with multiple groups, therapists with significant experience have found that having a program coordinator is essential; this individual should be both an effective therapist and administrator, serving as a vital communication link between therapists, clients, and colleagues. Collaborating with clinical teams on treatment decisions offers valuable opportunities to clarify group therapy selection criteria, while working with senior administrators can enhance the visibility of the group program and facilitate the acquisition of necessary resources, such as securing appropriately sized group rooms with flexible seating arrangements to encourage discussion and interaction. The goal of these guidelines is to foster the development of the field by providing resources for practitioners and informing the public about group psychotherapy practices.

Mars and Baker (2024) emphasize the importance of forming therapy groups and highlight that these groups often depend on referrals from other mental healthcare professionals, necessitating a broad referral base for effective operation. To address logistical challenges, they suggest that professionals managing multiple groups consider hiring a program coordinator. When establishing a group and managing referrals, therapists should evaluate several critical factors, including the group's purpose—whether it addresses a specific traumatic event, diagnosis, or skill set—and the degree of homogeneity or heterogeneity among members, ensuring sufficient similarity for group cohesion while also reflecting diversity to function as a microcosm of the outside world. Additionally, therapists must determine the duration of the group, which can be either close-ended or open-ended, with sessions typically lasting 90 to 120 minutes. The ideal group size is usually between 7 to 10 members, as too many participants can hinder discussions and dilute focus, while frequent changes in membership can disrupt cohesion and treatment effectiveness. The involvement of a co-therapist can enhance the experience by providing richer interactions and smoother logistics, while practical considerations such as the group's location, layout, and scheduling should ensure privacy and comfort for all members, often favoring a circular seating arrangement to promote inclusivity.

In their systematic review, Twomey and Dowling (2025) examine the relationship between group size, cohesion, and clinical outcomes in group psychotherapy, highlighting that despite its importance, this topic has received limited empirical attention. The review analyzed 17 studies, including meta-analyses, with a combined sample of 21,425 participants, revealing significant associations between group size and outcomes in seven studies, suggesting that smaller groups may yield better therapeutic results, particularly in process-oriented settings. However, the authors caution against relying solely on clinical opinions and traditional recommendations, as many group size guidelines have historically been based on anecdotal evidence rather than rigorous research. Notably, the findings indicate that groups with fewer than 9 members align with previously suggested optimal sizes, and there is little evidence to support the notion that smaller groups perform worse. The potential benefits of smaller groups may stem from enhanced social interactions and increased individual attention. Additionally, the review found that process-oriented groups exhibited a higher proportion of group-size associations compared to cognitive-behavioral therapy (CBT) groups, likely due to their focus on interaction and dynamics. Interestingly, group-size associations were more prevalent in clinical settings than in university or community contexts, possibly reflecting the varying functioning levels of participants. The review also noted that operationalizing group size continuously yielded more significant associations than categorical approaches, underscoring the need for more robust studies. While the review's methodological strengths include thorough database searches and quality assessments, it also highlights the necessity for higher-quality research to better understand the impact of group size on psychotherapy outcomes.

Taken together, the literature supports a pragmatic, context-sensitive approach to group design. Although empirical findings vary, converging evidence suggests that groups of approximately 6 to 9 participants often strike a balance between diversity of perspectives and depth of interpersonal engagement. Other research and clinical standards support some groups of up to 12 participants (Ezhumalai et al., 2018). Groups that are substantially smaller may lack critical mass for sustained interaction, whereas larger groups risk reduced cohesion and diminished individual participation unless carefully structured (Dueweke, 2022; Twomey & Dowling, 2025). Thus, group size should be regarded as a modifiable structural feature that interacts with cohesion, composition, and facilitation practices—rather than as a fixed parameter—to optimize therapeutic efficacy.

A growing body of evidence suggests that an ideal target of around 6 to 9 participants is optimal for most therapeutic groups, with some modalities allowing for up to 10 to 12 members. Research shows that groups exceeding 12 participants tend to experience diminished therapeutic effectiveness, along with increased risks to cohesion and individual engagement. Although there is no definitive "correct" group size, the prevailing evidence and guidelines strongly advocate for moderately sized groups designed to enhance interaction quality, foster cohesion, and improve facilitator effectiveness.

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Appendix

Patient Selection and Contraindications

Age is not an absolute contraindication for group psychotherapy; however, it is essential that the therapy is developmentally appropriate, as patients generally cannot participate effectively in groups that do not align with their developmental level. For example:

• Very young children (preschool age up to age 6) cannot engage in traditional verbal group psychotherapy. They require play-based or activity-based group formats instead, often individually;
• Children, adolescents, adults, and older adults should typically be placed in separate groups;
• Mixing wide age ranges (e.g., adolescents with adults or adults with elderly patients) is usually inappropriate due to:
  
  
  • Differences in cognitive development
  • Emotional maturity
  • Life experiences and roles
  • Communication styles and therapy goals.

Therefore, while most age groups can benefit from group therapy, individuals must be placed in age-homogeneous or developmentally matched groups. An age mismatch functions as a practical contraindication because it prevents meaningful participation and therapeutic cohesion.

Group psychotherapy requires that patients can attend regularly, communicate effectively, and tolerate interpersonal interaction. Populations that generally cannot participate effectively, or are temporarily inappropriate for group treatment, include:

• Acutely psychotic patients, especially those with prominent paranoia, hallucinations, or disorganized thinking
• Patients with severe cognitive impairment, such as advanced dementia or moderate to severe intellectual disability
• Individuals in acute mania, due to impulsivity, pressured speech, and poor behavioral control
• Patients who are intoxicated or in severe withdrawal from substances
• Those with imminent suicidal or homicidal risk requiring close individual monitoring
• Patients exhibiting severe aggression or an inability to control impulses that may endanger others
• Individuals with profound communication barriers (e.g., language mismatch, severe aphasia) that prevent participation
• Patients with extreme social anxiety or an inability to tolerate any interpersonal exposure, who may require individual therapy first

Many of these are temporary contraindications; once stabilized, patients may later benefit from group therapy.

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References