Co-occurring Addiction & Mental Illness


“To the extent that we respond to the health needs
of the most vulnerable among us, we do the most to
promote the health of the nation.”
—David Satcher, M.D., Ph.D., former U.S.
Surgeon General (News Hour, Jan. 21, 2002 )

Co-occurring mental illness and addiction are so common that you should enquire in every patient for the other disorder. These patients have often been neglected because they don’t fit neatly into mental health or addiction services. Historically, drug and alcohol services and mental health services were funded and managed separately. This leaves the patient struggling to find their way from one service to the other to meet their co-occurring needs.

In drug and alcohol service 75% of drug use patients and 85% of alcohol patients reported the presence of mental illness in the past 12 months (Weaver et al., 2003). They most commonly suffered from anxiety and depression, followed by personality disorders.

Table 1: Prevalence of mental illness in patients treated in drug and alcohol services

Drug Service Patients% Alcohol Service Patients%
Non-Substance Induced Psychotic Disorders 8 19
Personality Disorder 37 53
Affective/Anxiety Disorder 68 81
Psychiatric Disorder Present 75 85
High Potential for Referral 18 32

Source: Adapted from (Weaver et al., 2003)

Often, a patient develops an anxiety disorder and/or depression as an adolescent or young adult and subsequently discovers that sedating drugs such as alcohol, cannabis or opiates provide relief from debilitating dysphoria. With repeated use the anxiety and depression are made worse by the substance use and this can lead to more substance use eventually resulting in compulsively use despite the evidence of harm. This is the definition of addiction.

The patient may then seek treatment in a drug and alcohol service which neglects the driving force for the addiction namely the distressing anxiety/depression. If the opportunity for effective treatment is missed long enough the patient develops cognitive damage, that makes the addiction much more resistant to treatment. Alternatively, if the patient only receives treatment for their anxiety/depression and their addiction relapses the anxiety and depression will return. An integrated service that provides treatment for substance use and mental health problems concurrently is internationally recognized as the ideal treatment model.

The following table demonstrates the diagnosis and demographic characteristics of inpatients compared with outpatient and community samples of people seeking treatment.

Table 2: Proportion of psychiatric patients experiencing addiction problems in different settings

Client Variable Inpatient% Outpatient% Community%
Forensic History 29 10 8
Psychiatric Diagnosis
Mood Disorder 22 37 56
Anxiety Disorder 5 14 26
Schizophrenia 53 54 30
Personality Disorder 16 13 12
Substance use disorder 16 12 11
Higher Severity of Substance Use Disorder 28 19 18

Source: Adapted from Rush and Koegl, 2008

The prevalence of addiction problems among patients with mood disorders, anxiety disorders or schizophrenia in the community was high. Half of the community sample did not use any service, and the majority did not regard themselves as needing help (Andrews et al., 2001). When these patients with co-occurring disorders do seek treatment, the principal caregiver is usually the GP (Andrews et al., 2001).

Case example:

I recently treated a 45 year old female who had repeatedly failed treatment for her alcohol use disorder. She had attended alcohol services which had detoxified her and provided counselling but failed to notice the pattern of excessive spending, promiscuity and irritability since adolescence. With careful review it emerged that she had a Bipolar 2 Disorder and treating her with mood stabilisers in addition to anti-craving medication for her alcohol use disorder resulted in prolonged sobriety.


The rule is that mental illness and substance abuse co-occur. They are much more likely to both be present. Historically mental health and drug and alcohol services have ignored this. Stepped care is appropriate for the less severe illness but for co-occurring illness the ultimate treatment is an integrated approach.
Examining patients for co-occurring disorders is time-consuming and requires expertise. An in-patient admission provides the opportunity to examine the patient intensively for both their mental illness and addiction issues. A review of the entire psychiatric history, substance use and medical history with corroborative information from family and friends will result in the best treatment outcome. Engaging the patient in treatment by techniques such as motivational interviewing is important to increase engagement in treatment.

ANDREWS, G.,HENDERSON, S. & OF PSYCHIATRY, H.-W. 2001. Prevalence, comorbidity,
disability and service utilisation: overview of the Australian National Mental
Health Survey.
The British Journal of Psychiatry.
REGIER, D., FARMER, M. & RAES, D. 1990. Comorbidity of Mental Disorders with Alcohol and Drug
Abuse. Results from the Epidemiological Catchment Area Study.
Journal of the American Medical Association, 264, 2511-2518.
RUSH, B. & KOEGL, C. J. 2008. Prevalence and profile of people with co-occurring mental
and substance use disorders within a comprehensive mental health system.
The Canadian Journal of Psychiatry, 53, 810-821.
C., OF & TEAM, C. 2003. Comorbidity of substance misuse and mental illness
in community mental health and substance misuse services.
The British Journal of Psychiatry, 183, 304-313.

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