Causes of dual diagnosis

The reasons why people use will be as varied as the individuals themselves. Some may enjoy the experience, wish to improve their sex life or hope to lose weight. Others who are socially excluded may find a sense of community with other drug users.

For some, drug taking may be an escape from too much pressure. For others, it may be that boredom; peer pressure or a lack of opportunity is a trigger. Either way, it can be all too easy to create a vicious circle whereby using to escape problems only creates more problems and hence a greater need to escape.

There are many theories to explain why individuals with severe mental illnesses are vulnerable to the misuse of substances, and how the mental illness-substance misuse relationship co-exists. This is a summary of the key theories which seek to explain this complex relationship:

Self medication theory

This theory suggests that people with severe mental illnesses start to use a particular substance to relieve a specific set of symptoms and to deal with side effects of anti psychotic medication (Khantzian 1997).

This would mean that substances are not chosen at random, but are selected for their unique effects. For example, stimulants such as nicotine or amphetamines are used as ways to deal with sedation caused by high doses of certain types of antipsychotic medication.

On the whole, research appears to find no evidence in support of the self-medication theory; individuals did not use substances to alleviate specific symptoms of their psychiatric disorder, rather they appeared to use them for very similar reasons given by users who do not have symtoms of mental illness.

‘Alleviation of dysphoria’ theory

This theory simply means that individuals with severe mental illness often experience dysphoria (feeling bad) and that this makes them prone to using substances which alleviate (reduce) these feelings.

Research on self-reported reasons for using substances seems to support thes idea that the experience of these feelings is the primary motivator for drug and alcohol misuse (Pristach & Smith 1996).

Multiple risk factor theory

Although there is general support for the 'alleviation of dysphoria' (reducing bad feelings) theory, there are still many possible factors in the life of a person which make some one with a mental illness more at risk of using substances.

Mueser (1998) calls these ‘risk factors’ and they include:

  • Social isolation
  • Poverty
  • Lack of structured daily activity
  • Lack of adult role responsibility
  • Living in areas with high drug availability
  • Association with people who already misuse drugs

Other evidence suggests that past traumatic events, such as sexual abuse, are associated with the development of psychiatric problems and substance abuse. The experince of sexual abuse is high in individuals seeking help for mental health problems, especially in women, with one in every two women with dual diagnosis reporting past sexual abuse (Banerjee, Clancy, & Crome 2002).

'Supersensitivity' theory

This final theory proposed by Mueser et al. (1998) says that some people with severe mental illness have biological and psychological vulnerabilities, which are caused by genetic and early environmental events in their life.
This means that there is a particular vulnerability to stressful life events, so that experiencing something stressful will either cause a mental illness or trigger a relapse in an existing illness.

The theory states that although anti-psychotic medication can reduce the vulnerability, substance abuse may increase it, causing the individual to be more likely experience negative consequences from using relatively small amounts substances.

These individuals therefore, are “supersensitive” to the affects of certain substances. The supersensitivity theory provides a good explanation of why relatively low levels of substance use often result in negative consequences for individuals with severe mental illness (Mueser, Drake, &Wallach, 1998).