Dual Diagnosis Mental Illness and Substance Misuse

Dual Diagnosis Mental Illness and Substance Misuse

When someone with a mental health condition also misuses drugs, they
are said to have a ‘dual diagnosis’.  People with a dual diagnosis often
have poorer treatment outcomes than people who have a mental health
condition but who do not misuse substances and they may need additional

  • The term ‘dual diagnosis’ is used when someone has a  combination of mental health problems and alcohol or drug problems (‘substance misuse’).
  • The reason why someone may develop these problems together depends on the individual, but in many cases people use drugs or alcohol to ‘self-medicate’ in order to make symptoms of mental illness and side-effects of medication easier to handle.
  • Substance misuse occurs when use of alcohol or other drugs has a negative impact on someone’s functioning on a long-term basis.
  • It’s important that mental health and substance misuse services work together to make sure people with a dual diagnosis get adequate treatment and support. 


  • When someone has substance misuse problems on top of a mental health problem there can be increased risks, such as involvement with the criminal justice system.
  • In some circumstances, assertive outreach services should be considered for someone with a dual diagnosis. Assertive outreach services take a more proactive approach to treatment and support in the community. 

This factsheet covers:
1. What is dual diagnosis?
2. What is ‘substance misuse’ and what are the signs?
3. What are the possible effects of substance misuse?
4. How does dual diagnosis develop?
5. How can dual diagnosis be treated?
1. What is dual diagnosis?

The term ‘dual diagnosis’ is used to describe the situation where a person has been diagnosed with both a mental health condition and a problem with drugs (alcohol is considered to be a drug).  A person is still said to have a dual diagnosis even if they have multiple mental health conditions or problems with multiple drugs.  The term includes people who are addicted to drugs and those who misuse drugs but are not addicted.
It is estimated that up to half of people diagnosed with a mental health condition also misuse substances. People with a dual diagnosis are likely to have problems with their physical health, social functioning, money management, housing and are more likely to be in contact with the criminal justice system. The severity of a person’s mental health
condition as well as the extent of their drug misuse will determine how complex their needs are.
How does someone find out that they have a dual diagnosis?
The diagnosis of a mental health condition is made by a doctor. It is important that during an assessment the doctor considers the potential effect of substance misuse on a patient’s condition. Drugs can have effects that are similar to the symptoms of mental illness, and so it can be difficult for a doctor to distinguish which problems are due to the condition and which are due to substance misuse.  Full assessment is therefore important to ensure that a patient is not misdiagnosed.

2. What is ‘substance misuse’ and what are the signs?

Substance misuse is defined as intoxication by, or regular excessive consumption of and/or dependence on substances that have an effect on the brain, which leads to social, psychological, physical or legal problems. The most commonly misused drug is alcohol.
Signs of substance misuse can include:

  • Needing to increase the amount taken to get the same effect
  • Feelings of dependency or fear of stopping
  • Withdrawal symptoms if someone stops taking the drug for a short time. 
  • Sudden mood changes
  • Negative or changed outlook on life
  • Loss of motivation


  • Poor performance in work or education
  • Problems with relationships
  • Borrowing or stealing money from friends and family
  • Being secretive. 

3. What are the possible effects of substance misuse?

Substances can be divided into broad groups with a range of effects.
Stimulants (uppers) generally stimulate and speed up the central nervous system and cause people to feel more alert and awake. Stimulants include:

  •  Cocaine, amphetamines and ecstasy.

Depressants (downers) slow the central nervous system.  They might make someone sleepy, reduce heart rate, and reduce pain.  Depressants include:

  •  Alcohol and cannabis. Cannabis can also cause hallucinations. 

Sedative-Hypnotics (‘anxiolytic’, or anti-anxiety, drugs) are available medically on prescription but can be abused by people for their relaxing and calming effect.  Addiction, withdrawal and overdose can occur. Sedative hypnotics include:

  •   Benzodiazepines like diazepam (valium) and temazepam. 

Opiates and opioids can cause euphoria and provide relief from pain. There is high risk of dependence and withdrawal symptoms.  Opiates include:

  •  Heroin and morphine.

Volatile Substances can act as stimulants, but they are generally depressants.  They include:

  •  Solvents like glue, aerosols and lighter gas fuel. 

Hallucinogens can cause intensified sensations, paranoia, delusions, hallucinations and impaired judgement and reasoning. They include: 

  •  Ecstasy and LSD. 

Generally speaking, drug misuse can be detrimental to people for three main reasons:

  •  Someone could become addicted
  • The drug could cause someone physical or psychological harm
  • Drug misuse can have a negative impact on someone’s quality of life

4. How does dual diagnosis develop?

The relationship between mental health and substance misuse is complex and varies from individual to individual. The Department of Health has described four possible relationships:

  • A mental illness can lead to substance misuse. For example, a person may use alcohol or drugs to ‘self-medicate’ and relieve their symptoms, or their illness may make them more likely to engage in risky behaviour such as taking excessive amounts of drugs. 
  •  The use of alcohol or drugs can make a mental health condition worse or alter its course. For example, using substances may make people more likely to take part in risky behaviour or have worse psychotic symptoms.
  • Use of drugs or alcohol leading to psychological symptoms. 
  • Substance misuse or withdrawal may trigger mental health problems. For example there is some evidence that cannabis use increases the risk of developing a psychotic illness

It is likely that a range of factors make some people more vulnerable to mental health and/or substance misuse problems. This might include genetic factors, the impact of the environment someone grows up in or difficult or traumatic life events such as bereavement or abuse.
5. How can dual diagnosis be treated?

The treatment plan for dual diagnosis will vary depending on the mental health diagnosis and the substances that are being misused.  When dual diagnosis is treated, it is important that the care someone gets looks at both the mental health and substance misuse problems together.  The effect of substances on medication should be considered before a prescription is made.
Guidance14 published by Turning Point, a charity for people with complex needs, says:

  • There should be a local strategy for helping people with dual diagnosis
  • Assessments of people with dual diagnosis should take into account all of their needs and be carried out by a number of people working in different fields and employed by different agencies
  • Assessment should include a full history of someone’s mental health and substance use
  • A risk assessment should be carried out to see whether someone is a danger to themselves or to others


  • Treatment should be focused on engaging with a person, trying to motivate them to change their habits, preventing relapse and providing access to a range of treatments and helpful agencies

If you are worried about someone’s health and you want to try to get them help, the Rethink Mental Illness factsheet ‘Are you worried about someone’s mental health?’ looks at ways you can try. This is available to download at www.rethink.org/factsheets. You can also get a copy by contacting the Rethink Advice & Information Service directly (contact
details are at the end of this factsheet). 
Problems with the treatment of dual diagnosis

Despite it being common for people to have a combination of mental health and alcohol or drug problems, services for people with a dual diagnosis aren’t always adequate. Currently there aren’t many services specifically for people with dual diagnosis. This can result in people being passed between mental health and substance misuse services without getting proper treatment from either. For example a substance misuse service may say they are not trained to help people with mental health problems and mental health services might say they will not treat someone whilst they are using drugs or alcohol. 
Department of Health guidance is clear that staff from mental health services should be equipped to treat and support clients with a dual diagnosis. The Care Programme Approach (CPA) is the framework coordinating the care of people with complex mental health problems, including those with dual diagnosis, who are under secondary mental
health services. Guidance says that when a person’s care plan is drawn up detailing how their needs will be met, a risk management plan in relation to substance misuse should also be included and help with substance misuse should be put in place by the person’s care co- ordinator. The Department of Health regards people with dual diagnosis
to be a key group of people who should receive help under the CPA, providing their overall needs are high enough to meet the criteria.
Treatment of people with dual diagnosis can be difficult because their needs are complex and often long-term. Assertive outreach can be important because a lack of insight or awareness that there is a mental health problem and/or acceptance that there is a problem with alcohol or drugs can mean someone easily loses contact with services.
Further information on CPA and assertive outreach can be found in our factsheets ‘Care Programme Approach (CPA)’ and ‘Assertive Outreach’, which are available to download for free from www.rethink.org/factsheets or by contacting the Rethink Advice & Information Service directly. Contact details are at the end of this


Turning Point is a social care organisation working with individuals and their communities across England and Wales in the areas of drug and alcohol misuse, mental health and learning disabilities. They have particular expertise in working with people with dual diagnosis. 
Standon House
21 Mansell Street
E1 8AA

Tel: 020 7481 7600    Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it   Web: www.turning-point.co.uk 



Addaction is a drug and alcohol treatment agency. They have services in England and Scotland which deal primarily with drug and alcohol problems including support for families. 
67-69 Cowcross Street
Tel: 020 7251 5860  Web: www.addaction.org.uk 


Adfam is a national charity for families and friends of drug users. It offers confidential support and information. 
25 Corsham Street
N1 6DR
Tel: 020 7553 7640   Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it    Web: www.adfam.org.uk 



Al-Anon Family Groups is a service for families and friends of alcoholics. Al-Anon family groups provide understanding, strength and hope to anyone whose life is, or has been, affected by someone else's drinking.
Al-Anon Family Groups
61 Dover Street
Tel: 020 7403 0888    Open 10am-10pm, 365 days a year    Web: www.al-anonuk.org.uk 


Alcohol Concern is the national agency on alcohol misuse. They work to reduce the incidence and costs of alcohol-related harm and to increase the range and quality of services available to people with alcohol-related problems. 
64 Leman Street
E1 8EU
Tel: 020 7264 0510  Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it   Web: www.alcoholconcern.org.uk 



Alcoholics Anonymous is a fellowship of men and women who share their experience, strength and hope with each other that they may solve their common problem and help others to recover from alcoholism. They can provide a comprehensive list of private clinics around the country for drug, alcohol and other addictions on request. 
PO Box 1
10 Toft Green
Tel: 0845 769 7555  Web: www.alcoholics-anonymous.org.uk


Cocaine Anonymous is a fellowship of men and women who use the 12 step, self-help programme to stop cocaine and all other mind-altering substances. 
PO Box 46920
E2 9WF
Helpline: 0800 612 0225  10am – 10pm daily  Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it    Web: www.cauk.org.uk 


Drinkline is the national alcohol helpline. They provide information and self-help materials for help callers worried about their own drinking, and to support the family and friends of people who are drinking. They are confidential, you do not have to give your name and they can provide advice on where to get help.
Tel: 0800 917 8282 


DrugScope provides information and publications on a wide range of drug related topics. 
Prince Consort House
Suite 204 (2nd floor)
109/111 Farringdon Road
Tel: 020 7520 7550  Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it   Web: www.drugscope.org.uk


Frank (formerly National Drugs Helpline) is a campaign from the Department of Health and the Home Office which provides information and advice on drugs to anyone concerned about drugs and solvent misuse, including drug misusers, their families, friends and carers. 
Tel: 0800 77 66 00  Open 24 hours a day  Web: www.talktofrank.com


Narcotics Anonymous is a fellowship of men and women for who drugs has become a major problem. They have meetings all over the country. 
Helpline 0300 999 1212 Open 24 hours a day.   Web: www.ukna.org 



Release is a national 24-hour helpline offering advice and information on drug-related problems. They also have expertise in legal matters surrounding drugs.

388 Old street
Helpline: 0845 4500 215   Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it   Web: www.release.org.uk 



TASHA (tranquilisers, anxiety, stress help association) provides confidential information, support, training and counselling to individuals affected by mental health difficulties and problematic benzodiazepine use. 
Alexandra House
241 High Street Brentford
Tel: 0208 569 9933 Helpline (6pm – 9pm Mon-Wed): 0208 560 6601  Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Web: http://www.tasha-foundation.org.uk 


Information from http://www.rethink.org/document.rm?id=2440







Mental Health Foundation
Mental Health Foundation
The Royal College Of Psychiatrists