Key messages

  • Dual diagnosis of a mental illness and a substance abuse problem requires services to deal with both issues.
  • Dual diagnoses is common and requires services to take into account the complex nature of the problem.

People with dual diagnosis have both mental illness and drug and alcohol problems and disorders, and services in both these sectors must be able to respond to their needs.

In Victoria, as in other parts of the world, mental health and alcohol and other drug services are working with increasing numbers of people with dual diagnosis.

Dual diagnosis adds complexity to assessment, diagnosis, treatment and recovery, and can be associated with increased incidences of relapse.

Defining dual diagnosis

Dual diagnosis refers to one or more diagnosed mental health problems occurring at the same time as problematic drug and alcohol use.

A dual diagnosis condition can include:

  • a mental health problem or disorder leading to or associated with problematic alcohol and/or other drug use
  • a substance use disorder leading to or associated with a mental health problem or disorder
  • alcohol and/or other drug use worsening or altering the course of a person’s mental illness.

Dual diagnosis is an evolving field, both in understanding causal relationships and developing effective strategies for prevention, treatment and recovery.

Responding to people with dual diagnosis

Dual diagnosis demands an integrated approach to assessment and treatment in both specialist mental health and alcohol and other drug services.

Mental health and alcohol and other drug services should have the capacity to respond to the needs of people with dual diagnosis.

This means addressing an individual’s needs, according to the presenting illness, using a risk framework and understanding consumer and carer/family preferences. Staff should be trained in dual diagnosis and provided with appropriate education and learning opportunities.

Characteristics of people with dual diagnosis

Comorbidity of mental illness and substance use disorders is widespread, particularly among (but not exclusive to) young people.

People with a mental illness may use alcohol and other drugs episodically or continuously.

People also can use substances to reduce symptoms of their illness or the unwanted effects of their medication.

Many people with drug and alcohol problems have higher rates of mental illness than the general community, most commonly depression and anxiety.

Alcohol and drug use is also common among people experiencing psychosis and other serious mental illness.

Factors that contribute to the complexity of a diagnosis and response include:

  • the type, intent and frequency of drug use
  • the nature and severity of illness
  • the age of the individual
  • the physical and social impact of either or both disorders.

Illicit drug and alcohol use compounds a mental illness, even if the frequency and intensity of use do not meet the criteria for a substance use disorder.

Prevalence of dual diagnosis

Co-occurring substance use is common rather than exceptional among people with serious mental health problems and disorders.

Population health research shows high rates (up to 50 per cent) of alcohol and drug use among people with severe mental health problems.

Depression and anxiety are the most prevalent disorders co-occurring with drug and alcohol misuse, although rates of drug use among people with psychosis are also high.

Impacts on people with dual diagnosis

Service responses need to take into account the different and more complex impacts of dual diagnosis.

Research shows that compared with people with a single disorder (a mental illness or a substance use disorder), people with dual diagnosis have higher rates of:

  • severe illness course and relapse
  • violence, suicidal behaviour and suicide
  • infections and physical health problems
  • social isolation and family/carer distress
  • service use
  • anti-social behaviour and incarceration
  • homelessness.

Population-specific considerations for dual diagnosis

The following factors should be taken into account when screening, treating and managing people with dual diagnosis:

  • Young people with dual diagnosis are particularly at risk of experiencing poor outcomes. The age, stage of physical, neurological, psychological and social development makes young people more vulnerable.
  • Dual diagnosis presents specific challenges for Aboriginal people, who experience high rates of substance misuse.
  • Substance use among older people can have accentuated and profound impacts because of ageing physiology and reduced social interaction.
  • As well as differences across ages, the type and pattern of drug and alcohol use varies with culture, gender, peer group and social settings.