This Chapter reviews the relationship or comorbidity between ecstasy use and the use of other licit and illicit drugs, and mental disorders. “Comorbidity” has been defined as “any distinct clinical entity that has co-existed or that may occur during the clinical course of a patient who has the index disease under study” (p.456-7)1. Within psychiatry, comorbidity is commonly used to refer to the overlap of two or more psychiatric disorders2. In this Chapter we will discuss comorbidity between ecstasy and other drug use, and between ecstasy use and mental health problems. There are good reasons to examine links between ecstasy and other drug use problems or disorders. If they are likely to co-occur, this raises questions about the aetiology of the two types of drug use disorder. Prior to hypothesising about the mechanisms underlying comorbidity, patterns of comorbidity need to be carefully documented. Ecstasy acutely affects mood as detailed in Chapter Five. One review of the literature has concluded that chronic, heavy use of ecstasy is associated with sleep disorders, depressed mood, persistent elevation of anxiety, impulsiveness and hostility3. If such associations exist, does ecstasy use play a causal role in the development of these disorders? Not all studies have found associations between ecstasy use and mental health4 5 and most studies have been cross sectional.
If there is comorbidity between ecstasy and other drug use problems, and ecstasy use and mental disorders, this may have important implications for assessment and treatment. Persons with comorbid panic disorder and substance use disorders, for example, are more likely to have a chronic disorder, a higher risk of suicidal behaviour, and poorer social functioning6. There are also implications for public health policy: if two problems are likely to co-occur this has implications for the types of service offered. Specifically, it means that drug treatment services for persons with problematic ecstasy use may also need to address comorbid drug use and mental health problems. This is particularly the case if persons with co-occurring drug use disorders have a worse clinical outcome than those with a single disorder.