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Dual diagnosis

Drug abuse with other psychiatric conditions

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find one of our health articles more useful.

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What is a dual diagnosis?

Dual diagnosis is the term used to describe patients with both severe mental illness and problematic drug and/or alcohol use. The term originated from the USA in the 1980s and has been adopted in the UK more recently. It can also be described as co-occurring disorders and has been broadened to include any addictive behaviour.1 The nature of the relationship between the two conditions is well established and may be genetically linked.2

  • A primary psychiatric illness may precipitate or lead to substance misuse.3 Patients may feel anxious, lonely, bored, have difficulty sleeping or may want to 'block out' symptoms or medication side-effects.

  • Substance misuse may worsen or alter the path of a psychiatric illness.

  • Intoxication and/or substance dependence may lead to psychological symptoms.

  • Substance misuse and/or withdrawal may lead to psychiatric symptoms or illness. It may act as a trigger in those who are predisposed.4

The importance of making the diagnosis

People with dual diagnosis have complex needs relating to health, social, economic and emotional stressors or circumstances which can often be exacerbated by their substance misuse.5 Efforts to provide support for individuals with a dual diagnosis presents a major challenge.

In 2009, the Department of Health and the Ministry of Justice issued guidance on the management of dual diagnosis in prisons which remains in place in 2023.6

The principles of dual diagnosis management are stated within the National Institute for Health and Care Excellence (NICE) 2016 guidance and are developed in other agencies' handbooks of care. Turning Point (the UK's leading social care organisation) has produced a good practice guide for practitioners working with individuals with substance use and mental health issues.7 Its purpose is to help practitioners to plan, organise and deliver services for people with dual diagnosis. It contains case studies from services working with people with a dual diagnosis in a range of settings and localities, offering practical help for those wanting to establish dual diagnosis services.

This is a complex area of care and issues involved are:

  • Harm reduction: supervised consumption, needle exchanges, looking at wider health needs (eg, hepatitis and HIV exposure).

  • Stabilising consumption: establishing treatment programmes (detoxification, substitute prescribing, counselling and psychological treatments).

  • Education: improving awareness of risk-taking behaviour, explaining how to find support.

  • Addressing social care needs including possible triggers for substance misuse.

  • Treatment of mental health problems: drug treatment, psychosocial therapy, complementary therapies.

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The role of primary care (first contact)

Identify and provide support people with coexisting severe mental illness and substance misuse and meet their immediate needs, wherever they present:5

  • Look out for multiple needs (including physical health problems, homelessness or unstable housing)

  • Remember that they may find it difficult to access services because they face stigma.

  • Remember they may have a range of chronic physical conditions and that their condition may cause them to relapse, or affect these conditions.

  • Provide support to access other services as needed, such as housing or benefits.

  • Remember to consider the safeguarding needs of this group.

  • Refer to secondary care mental health services and follow up; ensure they take the lead for assessment and care planning.

Be mindful that communication difficulties can present barriers to successfully engaging these individuals.8

Secondary care principles

  • Do not exclude people from care based on their substance misuse needs.

  • Undertake a full assessment of the individual's physical, mental health and substance misuse needs.

  • Provide a care co-ordinator who will act as a point of contact for the individual and their famillies or carers.

  • Develop a care plan in collaboration with the individual and share it with family/carers.

  • Liaise with other services to address the other needs.

  • Arrange annual multi-agency, multi-disciplinary reviews to assess needs and progress.

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The scale of the problem

Accurate estimates of prevalence can bee difficult to come by, because studies have used different diagnostic criteria and terminology frequently changes.9

The 2002 Comorbidity of Substance Misuse and Mental Illness Collaborative study (COSMIC) concluded that:10

  • 75% of drug service clientele and 85% of alcohol service clientele had mental health problems.

  • 44% of mental health service users used drugs or alcohol at hazardous or harmful levels in the previous year.

Reviews of co-occurring major depression and substance use found prevalences between 12-80%.11

A 2021 systematic review and meta-analysis looking at the health of people with co-occurring substance misuse and mental health problems found that from 444 included articles, 31% of data points included prison terms and substance use and 27% of data points involved substance use and severe mental illness.12 These groups were often subject to health inequalities and exclusionary practices and experienced raised all-cause mortality.

There is a high prevalence of dual diagnosis among prison inmates, with studies quoting prevalence between 18-56%.13

The European Schizophrenia Cohort found that the lifetime rate for people with schizophrenia who were dependent on alcohol or other psychoactive substances was highest in the UK (35%) and considerably lower in Germany (21%) and France (19%).14

A study of comorbid substance abuse in psychosis concluded that rates varied depending on service settings, geographical areas and ethnicity. Rates between 20% and 37% were reported in mental health settings, while figures in addiction settings were less clear (6-15%). They were especially high in inpatient and crisis team settings (38-50%) and forensic settings. Rates were highest in inner city areas.15

Differential diagnosis

The symptoms of drug or alcohol misuse can be very similar to the symptoms of mental illness, and vice versa, and they frequently co-exist.16 This can make it difficult to make a confident dual diagnosis. When differentiating between a primary psychotic and a substance-induced disorder, consider:

  • Did psychosis precede the onset of substance abuse?

  • Does psychosis persist for longer than one month after acute withdrawal or severe intoxication?

  • Are the psychotic symptoms consistent with the substance used?

  • Is there a history of psychotic symptoms during periods of abstinence?

  • Is there a personal or family history of a non-substance-induced psychotic disorder?

Substances which induce psychotic symptoms resulting from substance misuse include:

  • Cannabis: intoxication can induce a transient, self-limiting psychotic disorder characterised by hallucinations and agitation.

  • Psychostimulants such as amfetamines: when used over prolonged periods these can produce a psychotic picture similar to schizophrenia.

  • Hallucinogens: psychosis induced by these is usually transient but can persist with sustained use.

  • Alcohol - heavy use: this is associated with morbid jealousy and alcoholic hallucinations. Withdrawal from alcohol may also provoke psychotic symptoms.

Complications of a dual diagnosis

Dual diagnosis is associated with:17

  • Worsening psychiatric symptoms.

  • More frequent rehospitalisation or longer in-patient stays.

  • Poor physical health.18

  • Poor medicine adherence.19

  • Homelessness and poverty.

  • Increased risk of HIV infection.

  • Poor social outcome (including impact on family, education, carers and employment).

  • A personal history of sexual abuse.

  • Financial pressures.

  • Increased risk of violence and contact with the criminal justice system.20

  • Increased risk of self-injury or suicide.19

  • Isolation and social withdrawal.

  • Risk of prison service.

  • Higher all-cause mortality.12

The future

Twenty years on, the situation does not seem to have improved. Health inequalities for many have worsened. Organisations like Turning Point aim to deliver innovative integrated care in communities, specialising in substance misuse, mental health, learning disability, employment services, criminal justice, primary care and public health. They work with commissioners, GPs, clinicians and communities, to help understand the needs of the people needing support, trying to find new ways to engage even the hardest to reach people.

Further reading and references

  1. Picello A, Ducci G; Editorial: Clinical practices for co-occurring psychiatric and addictive disorders. Front Psychiatry. 2022 Dec 20;13:1097424. doi: 10.3389/fpsyt.2022.1097424. eCollection 2022.
  2. Di Lorenzo R, Galliani A, Guicciardi A, et al; A retrospective analysis focusing on a group of patients with dual diagnosis treated by both mental health and substance use services. Neuropsychiatr Dis Treat. 2014 Aug 11;10:1479-88. doi: 10.2147/NDT.S65896. eCollection 2014.
  3. Kock P, Meyer M, Elsner J, et al; Co-occurring Mental Disorders in Transitional Aged Youth With Substance Use Disorders - A Narrative Review. Front Psychiatry. 2022 Feb 24;13:827658. doi: 10.3389/fpsyt.2022.827658. eCollection 2022.
  4. Frisher M, Crome I, Macleod J, et al; Substance misuse and psychiatric illness: prospective observational study using the general practice research database. J Epidemiol Community Health. 2005 Oct;59(10):847-50. doi: 10.1136/jech.2004.030833.
  5. Coexisting severe mental illness and substance misuse: community health and social care services; NICE guidance (November 2016)
  6. A Guide for the Management of Dual Diagnosis for Prisons, Dept of Health and the Ministry of Justice, 2009
  7. The SUMH Resource Pack; Working with people with coexisting Substance Use & Mental Health (SUMH) issues: A good practice guide for practitioners, Turning Point
  8. Wu K, Baker J; Patient Communication In Substance Abuse Disorders.
  9. The Co-Existence of Mental Health Needs and Substance Misuse (Dual Diagnosis) Care Pathway Liaison & Referral Protocol; North Essex Partnership NHS Foundation Trust, 2011
  10. Weaver T, Madden P, Charles V, et al; Comorbidity of substance misuse and mental illness in community mental health and substance misuse services. Br J Psychiatry. 2003 Oct;183:304-13. doi: 10.1192/bjp.183.4.304.
  11. Tirado Munoz J, Farre A, Mestre-Pinto J, et al; Dual diagnosis in Depression: treatment recommendations. Adicciones. 2018 Jan 1;30(1):66-76. doi: 10.20882/adicciones.868.
  12. Tweed EJ, Thomson RM, Lewer D, et al; Health of people experiencing co-occurring homelessness, imprisonment, substance use, sex work and/or severe mental illness in high-income countries: a systematic review and meta-analysis. J Epidemiol Community Health. 2021 Oct;75(10):1010-1018. doi: 10.1136/jech-2020-215975. Epub 2021 Apr 23.
  13. Young JT, Heffernan E, Borschmann R, et al; Dual diagnosis of mental illness and substance use disorder and injury in adults recently released from prison: a prospective cohort study. Lancet Public Health. 2018 May;3(5):e237-e248. doi: 10.1016/S2468-2667(18)30052-5. Epub 2018 Apr 18.
  14. Carra G, Johnson S, Bebbington P, et al; The lifetime and past-year prevalence of dual diagnosis in people with schizophrenia across Europe: findings from the European Schizophrenia Cohort (EuroSC). Eur Arch Psychiatry Clin Neurosci. 2012 Oct;262(7):607-16. doi: 10.1007/s00406-012-0305-z. Epub 2012 Mar 17.
  15. Carra G, Johnson S; Variations in rates of comorbid substance use in psychosis between mental health settings and geographical areas in the UK. A systematic review. Soc Psychiatry Psychiatr Epidemiol. 2009 Jun;44(6):429-47. Epub 2008 Nov 13.
  16. Lubman DI, Sundram S; Substance misuse in patients with schizophrenia: a primary care guide. Med J Aust. 2003 May 5;178 Suppl:S71-5.
  17. Chakraborty R, Chatterjee A, Chaudhury S; Impact of substance use disorder on presentation and short-term course of schizophrenia. Psychiatry J. 2014;2014:280243. doi: 10.1155/2014/280243. Epub 2014 Apr 2.
  18. Subodh BN, Sharma N, Shah R; Psychosocial interventions in patients with dual diagnosis. Indian J Psychiatry. 2018 Feb;60(Suppl 4):S494-S500. doi: 10.4103/psychiatry.IndianJPsychiatry_18_18.
  19. Blachut M, Scislo P, Jarzab M, et al; Impact of dual diagnosis in patients with schizophrenia and affective disorders during hospital treatment on the course of illness and outcomes of treatment - a preliminary report. Psychiatr Pol. 2019 Dec 31;53(6):1237-1250. doi: 10.12740/PP/OnlineFirst/103352. Epub 2019 Dec 31.
  20. Soyka M; Substance misuse, psychiatric disorder and violent and disturbed behaviour. Br J Psychiatry. 2000 Apr;176:345-50.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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