Cristina L. Isaacs, Fielding's School of Psychology (2012)
Substance abuse and addiction are complex phenomena, in part due to the complexity of drug abuse and the co-occurrence of mental illness. Opiates, stimulants, sedatives, and hallucinogens produce a unique series of pharmacological effects on the brain.
This study examined the relationship between psychiatric disorder and the chosen substances of use. It was expected that substances of use would not be evenly distributed across psychiatric illness categories. This was based on the premise that psychiatric disorders and specific substances of use are not randomly associated, but that people with specific disorders may prefer certain types of substances, assumedly, but not necessarily, because it reduces the perception of the negative consequences of their disorder. It was anticipated that, for the mentally ill, the substance of abuse chosen will be related to their mental health problems.
However, it was found that there was no differentiation of substance rates based on psychiatric disorder. The results found absolutely no relationship between the symptoms of psychiatric disorder (depression, anxiety, thought disorder, or executive disorder) and substances of use. In fact, the observed values were almost identical to the expected values, indicating that the type of substance of choice is orthogonally related to the symptoms of psychiatric disorder. No group of substances was preferred over the others for any disorder. Therefore, the results of this study did not support a conclusion that the substance used by a mentally ill person would be specific to the psychological illness of the person. In addition, the increased likelihood that the substance user who also presents with a mental illness will use more than one substance, as this research has determined, makes the ability to detect differences in drug effects on the illness that much more difficult.