Substance use disorders, depression and social phobia: An examination of co-occurring disorders

Abstract

Substance use disorders (SUDs), mood, and anxiety disorders are highly prevalent and often co-occur. Little research has comprehensively examined the comorbidity of mood and anxiety disorders among people with SUDs, particularly in relation to two of the most commonly co-occurring disorders, depression and social phobia.

Study One involved an epidemiological investigation into the prevalence and correlates of mood and anxiety disorders among SUDs in the Australian general population. There was a high prevalence, and complex patterns, of individual disorders among those with SUDs. Individuals with a SUD plus one or two comorbid disorder classes exhibited significantly poorer health and wellbeing compared to those with a pure SUD.

The remaining studies were undertaken using a sample of 132 depressed individuals in treatment for SUDs. Study Two investigated the prevalence and correlates of social phobia among this cohort. Three-quarters (72.3%) met DSM-IV-TR criteria for past-month social phobia, and experienced a more severe clinical profile compared to those with no social phobia. Individuals who related their fears to co-occurring disorders (i.e., disorder-related social phobia) had a poorer clinical presentation than those who did not (i.e., ‘pure’ social phobia).

Study Three examined the longitudinal outcomes of this cohort based on social phobia diagnostic status. Despite greater severity at baseline, individuals with social phobia experienced greater improvements in some substance use and mental health characteristics over 12-months. This improvement was primarily driven by those with ‘pure’ social phobia; those with disorder-related social phobia consistently experienced poorer outcomes over time.

Study Four explored the prevalence, predictors, and outcomes of persistent social phobia. Persistence was common (35.4%) and was predicted by unemployment, and more severe social phobia features and mental health characteristics. Individuals with persistent social phobia had poorer outcomes at 12-months than those with non-persistent social phobia.

This thesis emphasises the complexity of comorbidity associated with SUDs and highlights the need for routine assessment of both ‘pure’ and disorder-related social phobia among depressed individuals in treatment for SUDs. Further research is needed to determine how best to treat this comorbidity. Given the poorer outcomes associated with persistent social phobia, a stepped-care approach may be appropriate.