There is considerable debate surrounding the appropriateness of using a single category for a heterogeneous group of individuals with complex needs and a varied range of problems.
They have increased rates of relapse, hospitalization, homelessness, and HIV and hepatitis C infection compared to those with either mental or substance use disorders alone.
[5] The identification of substance-induced versus independent psychiatric symptoms or disorders has important treatment implications and often constitutes a challenge in daily clinical practice.
In some cases, these substance induced psychiatric disorders can persist long after detoxification, such as prolonged psychosis or depression after amphetamine or cocaine use.
Among the currently prevalent medications, benzodiazepines are the most notable drug for inducing prolonged withdrawal effects with symptoms sometimes persisting for years after cessation of use.
Structured instruments, as Global Appraisal of Individual Needs - Short Screener-GAIN-SS and Psychiatric Research Interview for Substance and Mental Disorders for DSM-IV-PRISM,[9] have been developed to increase the diagnostic validity.
The 2011 USA National Survey on Drug Use and Health found that 17.5% of adults with a mental illness had a co-occurring substance use disorder;[11] this works out to 7.98 million people.
[13] A study by Kessler et al. in the United States attempting to assess the prevalence of dual diagnosis found that 47% of clients with schizophrenia had a substance misuse disorder at some time in their life, and the chances of developing a substance misuse disorder was significantly higher among patients with a psychotic illness than in those without a psychotic illness.
[14][15] Another study looked at the extent of substance misuse in a group of 187 chronically mentally ill patients living in the community.
[17] Wright and colleagues identified individuals with psychotic illnesses who had been in contact with services in the London borough of Croydon over the previous 6 months.
For this reason, the DSM-IV advises that diagnoses of primary psychiatric disorders not be made in the absence of sobriety (of a duration sufficient to allow for any substance-induced post-acute-withdrawal symptoms to dissipate) up to 1 year.
[12] Clients with co-occurring disorders face challenges accessing treatment, as they may be excluded from mental health services if they admit to a substance use problem and vice versa.
[23][24] The Substance Abuse and Mental Health Services Administration in the United States describes integrated treatment as being in the best interests or clients, programs, funders, and systems.
A 2019 Cochrane meta-analysis that included 41 randomized controlled trials found no high-quality evidence in support of any one psycho-social intervention over standard care for outcomes such as remaining in treatment, reduction in substance use and/or improvement in global functioning and mental status.
[39][40][41][42] The self-medication theory suggests that people with severe mental illnesses misuse substances in order to relieve a specific set of symptoms and counter the negative side-effects of antipsychotic medication.
Some studies show that nicotine administration can be effective for reducing motor side-effects of antipsychotics, with both bradykinesia[44] (stiff muscles) and dyskinesia[45] (involuntary movement) being prevented.
[47][48] Other evidence suggests that traumatic life events, such as sexual abuse, are associated with the development of psychiatric problems and substance use.
[49] The supersensitivity theory[50] proposes that certain individuals who have severe mental illness also have biological and psychological vulnerabilities, caused by genetic and early environmental life events.
Although there are limitations in the research studies conducted in this area, namely that most have focused primarily on schizophrenia, this theory provides an explanation of why relatively low levels of substance misuse often result in negative consequences for individuals with severe mental illness.
[50] Current nosological approach does not provide a framework for internal (sub-threshold symptoms) or external (comorbidity) heterogeneity of the different diagnostic categories.
[54] During the mid-1980s, a number of initiatives began to combine mental health and substance use disorder services in an attempt to meet this need.