Family Therapy

Family Therapy and the Diathesis-Stress Model

Family therapy for schizophrenia and the diathesis-stress model represent complementary developments — the model provides the theoretical framework for understanding how biological vulnerability and psychosocial factors interact to produce and maintain schizophrenia, whilst family therapy addresses one of the most important modifiable psychosocial stressors (expressed emotion) in clinical practice.

The Diathesis-Stress Model (Zubin and Spring, 1977)

The diathesis-stress model, proposed by Zubin and Spring (1977) and developed by Gottesman and Shields (1982) in the context of schizophrenia, proposes that schizophrenia (and other mental disorders) arise from the interaction of two factors:

Diathesis: a biological or psychological predisposition or vulnerability — constituted by genetic risk, prenatal neurodevelopmental disruptions, or early adverse experiences that have altered brain development. The diathesis alone is insufficient to produce schizophrenia.

Stress: environmental stressors — psychosocial adversity, life events, high-EE family environments, substance use, social defeat — that, in combination with the diathesis, trigger the onset or relapse of disorder.

The model proposes a threshold: disorder emerges when the combined weight of diathesis and stress exceeds the individual's threshold for breakdown. Crucially, the threshold varies — individuals with high diathesis require little stress to develop disorder; individuals with low diathesis may only develop disorder under extreme stress (or not at all).

Implications of the Diathesis-Stress Model

The model has several important implications. First, it explains why only some individuals with genetic risk develop schizophrenia — those with high genetic risk but low stress exposure may never cross the threshold. Second, it explains why life events and psychosocial stressors are more likely to precipitate psychosis in individuals with biological vulnerability than in the general population. Third, it is non-deterministic — biological vulnerability is not destiny; reducing psychosocial stressors can prevent disorder even in high-risk individuals. Fourth, it integrates biological and psychological explanations rather than treating them as competing alternatives.

Family Therapy for Schizophrenia

Family therapy in schizophrenia is specifically designed to reduce expressed emotion (EE) — the most evidence-based psychosocial risk factor for relapse. The main elements, as described by Leff et al. (1982) and Pharoah et al. (2010), include:

• Psychoeducation: providing family members with accurate information about schizophrenia — its nature, causes, course, and treatment. Reducing misattributions of symptoms to laziness or wilfulness reduces critical comments.
• Communication skills training: teaching family members to communicate in less critical and less over-involved ways. Includes active listening, expressing concern without criticism, and setting appropriate limits.
• Problem-solving skills: helping families develop structured approaches to managing crises and challenges, reducing escalating frustration.
• Reducing face-to-face contact (where high EE and high contact combine): in some cases, encouraging the patient to spend time outside the home reduces the risk associated with extended high-EE contact.

Pharoah et al. (2010) Cochrane review of 53 RCTs found that family intervention significantly reduced relapse rates compared with standard care (approximately 20% absolute reduction at 12 months) and reduced hospital admission, with positive effects on patient adherence to medication and family wellbeing.

The diathesis-stress model provides the theoretical rationale for family therapy: by reducing the psychosocial stress (EE) acting on biologically vulnerable individuals, family therapy reduces the likelihood of threshold-crossing and relapse.