How are mental illness and substance abuse related to one another? Some models propose that increased mental illness causes subsequent worsening substance abuse. Other models propose the reverse, namely that increased substance abuse causes subsequent worsening mental illness. Yet other models propose a reciprocal relationship between the two in which each influences the other in a dynamic feedback process.

These models often serve as the guiding philosophy for dual diagnosis treatment programs. Programs that adopt the first model incorporate intensive psychological diagnostic assessment and psychological and psychiatric treatment by qualified licensed mental health professionals as a central part of the program, accompanied by chemical dependency education, programming, and community support.

Programs that adopt the second model are centered on intensive sobriety programming, often 12-step based, primarily delivered by unlicensed chemical dependency counselors. These programs may or may not include limited mental health diagnosis and treatment by licensed mental health professionals.

Programs that adopt the third model are centered on a mixed programming model in which mental health and chemical dependency programming are more balanced and where group therapy often led by trainees or interns may be emphasized at the expense of individual therapy and individual medication management by licensed mental health professionals.

Scientific Support for the Primary Mental Illness Model

A recent study published in England finds scientific support for the first model but not for the second and third models. This study evaluated the relationship between mental health status and alcohol use patterns in a group of 500 predominantly male untreated heavy drinkers over a span of 10 years. Study participants reported their drinking patterns and mental health status every two years. At each two year assessment, drinking patterns were measured by the reported number of “heavy drinking” days per month over the previous 12 months. Mental health status was determined by completion of a mental health questionnaire, with higher scores indicating better mental health.

The results of the study found that mental health status predicted changes in drinking patterns over time. Results did not support the model that changes in drinking patterns predicted mental health status over time. Frequency of heavy drinking days did not predict subsequent changes in mental health scores. Data analysis also did not support the reciprocal model in which mental health changes and drinking pattern changes mutually influenced one another over time.

Those who had poorer mental health scores subsequently increased their frequency of heavy drinking, and those with better mental health scores subsequently reduced their frequency of heavy drinking. The authors conclude that “mental health is likely to be the dominant underlying process in the dynamic system.” (p. 692). These study findings are consistent with those of research on more moderate drinkers which find that mental health issues are a significant risk factor for subsequent alcohol abuse.

Implications for Choosing a Primary Mental Health Dual Diagnosis Treatment Program

Taken as a whole, these findings are supportive of dual diagnosis treatment programs that have a central focus on aggressive diagnosis and treatment of mental health conditions by qualified licensed mental health professionals and supervised interns. Psychological assessment should be conducted to evaluate for bipolar disorder, depression, anxiety disorders, psychosis, schizophrenia, schizoaffective disorder, attention-deficit hyperactivity disorder (ADHD), and other psychiatric disorders. Individual, group, and family therapy, medication management, and community interventions focused on the patient’s specific diagnosis all should be key components of optimal dual diagnosis treatment. Substance abuse education and information also must be incorporated throughout this programming, and specific substance abuse groups and community resources based on SMART Recovery and/or 12-Step should be included in the program.


Bell, S., Orford, J. et al. (2015). Heavy drinking days and mental health: An exploration of the dynamic 10year longitudinal relationship in a prospective cohort of untreated heavy drinkers. Alcoholism: Clinical and Experimental Research, 39 (4), 688-696.