Drug addiction and substance use disorder: signs, causes and treatment

Key points

• Drug addiction, or substance use disorder, is a health condition. Dependence involves tolerance and withdrawal, not a lack of willpower [2].
• Use, harmful use and dependence differ: harmful use causes harm without the physical features of dependence [3].
• Substance use and mental health worsen each other: 72% of adults starting treatment in England in 2023 to 2024 had a mental health treatment need [5].
• Local drug services are free, confidential and take self-referrals, and stopping is not a condition of help [1][10].
• Stopping alcohol or benzodiazepines suddenly can be dangerous without medical help [7][8].
• Naloxone reverses opioid overdose and can be supplied without a prescription by drug services [6].

What drug addiction is

Drug addiction, known clinically as substance use disorder, is a health condition in which a person loses control over their drug use and keeps using despite harm. The NHS describes addiction as not having control over doing, taking or using something to the point where it could be harmful [2].

If you need help now. Samaritans: call 116 123, free, 24/7. Shout: text SHOUT to 85258. NHS 111, then choose the mental health option. Call 999 if anyone is in immediate danger, including a suspected overdose. FRANK: call 0300 123 6600 or text 82111 for free, confidential drug advice and to find local services [10].

No reliable UK prevalence figure exists, as most people affected never reach services. In England, 310,863 adults were in drug and alcohol treatment in 2023 to 2024 [5], against an estimated 300,000 opiate and crack users alone [9].

Symptoms

Signs build gradually across several parts of life.

Physical

• Tolerance: needing more for the same effect [2].
• Withdrawal: feeling unwell, agitated or sleepless when the substance wears off [2].

Behavioural

• Using more, or for longer, than intended, with time organised around getting and recovering.
• Attempts to cut down that do not hold, and use continuing after problems appear [3].

Psychological

• Strong urges or cravings, and secrecy about use [2].
• Low mood or irritability that lifts briefly with use and returns worse.

Commonly confused with. Depression and anxiety disorders, which cause similar low mood and poor sleep, and untreated ADHD, where restlessness and poor concentration look like drug effects.

Types

Substance use is described as three situations rather than subtypes, and the difference decides what help is useful.

• Use. Taking a substance without significant harm. NG64 excludes occasional or experimental adult use from its definition of drug misuse [3].
• Harmful use. Regular excessive consumption causing physical, mental or social harm, without the features of dependence [3].
• Dependence. Harm plus loss of control, tolerance and withdrawal [2][3]. Reversing it usually needs medical or psychological support rather than effort alone.

Causes and risk factors

There is no single cause, and no test predicting who will become dependent. The NHS points to unemployment, poverty, stress and pressure at work, and to using a substance to block out difficult experiences [2].

• The substance itself, which changes how a person feels and creates a strong urge to use again [2].
• Genetics, which carry part of the risk, alongside environmental factors such as being around other people with addictions [2].
• Groups named in NG64 as higher risk, including people with mental health conditions, looked-after children and care leavers [3].

Mental health runs in both directions. Substances are often used to manage anxiety, low mood, the after-effects of trauma and ADHD symptoms, and they do reduce distress briefly. Over time they worsen all of those, as sleep, mood and concentration deteriorate and withdrawal produces anxiety of its own. The 2021 government review concluded that trauma and mental ill health drive much addiction [9].

How it is diagnosed

There is no blood test for addiction. A GP or a local drug and alcohol service can assess drug use, and a psychiatrist may be involved where a mental health condition is present.

A first appointment covers drug use, work, family and housing, and urine or saliva testing is sometimes used [1]. Staff set out the options, agree a plan and assign a keyworker [1]. It commits nobody to stopping or to medication. Of people starting treatment in England in 2023 to 2024, 99% did so within three weeks [5].

Dual diagnosis. Where a substance use disorder and a mental health condition are both present, this is called dual diagnosis. UK services have historically handled the two separately, and people have been turned away from mental health services until the drug use is resolved, and from drug services because of the mental illness [9]. NG58 asks services to support these people wherever they present, and notes that stigma makes services harder to reach [4].

Treatment

Treatment comes mainly from local drug and alcohol services, at home, in hospital or in residential rehabilitation [1]. NG64, published 22 February 2017, is a prevention guideline: it focuses on identifying people at risk early and preventing use from escalating [3].

What treatment involves [1]:

• Talking therapies, mainly cognitive behavioural therapy, which looks at thoughts and behaviour.
• Substitute medication such as methadone or buprenorphine for opioid dependence, reducing withdrawal and reliance on street drugs. Doses are for a prescriber.
• Detoxification, support for stopping completely.
• Self-help groups such as Narcotics Anonymous and SMART Recovery.
• Testing and treatment for hepatitis and HIV.

Abstinence is not required. Services also support people who want advice, or to reduce use, rather than stop [1].

Overdose and naloxone. Naloxone is the emergency antidote for overdose caused by heroin and other opioids, and reverses the breathing difficulties it causes [6]. Since December 2024 it can be supplied without a prescription by drug services and others, to people at risk and to their family or friends, and anyone can use naloxone to hand to save a life [6].

Stopping suddenly can be dangerous. It is very dangerous to stop drinking suddenly if a person is dependent on alcohol, and withdrawal can include seizures, hallucinations and confusion [7]. Benzodiazepines such as diazepam also cause withdrawal if stopped suddenly, and doses are normally reduced gradually under medical supervision [8].

Living with drug addiction

Contact with a service is the step that opens everything else up, and you do not have to have stopped first.

• Use the keyworker, who coordinates your care and is who to tell when something is not working [1].
• Ask about naloxone if you or someone close to you uses opioids; family and friends can be given it [6].
• If you also have depression, anxiety, PTSD or ADHD, say so at the drug service and your GP, and ask them to contact each other [4].
• Never stop alcohol or benzodiazepines abruptly on your own [7][8].

Stigma and fear of consequences. Fear of being judged, and of what happens if the wrong person finds out, is the main reason people delay asking for help. Parents worry about losing their children, and people in work worry about their job. Employers are often wary of hiring people with a history of drug problems [9], and NICE recognises that stigma makes services harder to reach [4]. Those fears are reasonable, but untreated dependence gets worse, and you can ask what a service records before giving details.

When to speak to a professional

Speak to your GP or a local drug service if any of this applies.

• You are using more than you intended, or find it hard to stop once you start.
• It is affecting your work, relationships, money or health.
• You feel physically unwell when the substance wears off.
• You are using a substance to manage anxiety, low mood or unwanted memories.

No GP referral is needed. You can approach a local drug service yourself [1], or call FRANK on 0300 123 6600, text 82111, or find services at talktofrank.com [10].

Call 999 if someone has collapsed, cannot be woken, is breathing slowly or not at all, or has had a seizure. Tell the crew what was taken [10].

Common questions

Is drug addiction a mental health condition?

Yes. It is treated as a health condition in the NHS, and people with drug problems are entitled to treatment like anyone with another health problem [1]. Of adults starting treatment in England in 2023 to 2024, 72% reported a mental health treatment need [5].

Do you have to stop using drugs before you can get help?

No. NHS drug services support people who want advice, people who want to reduce their use, and people who want to stop [1]. Stopping is not a condition of being seen.

Is asking for help confidential?

Local drug services in England offer confidential information, advice and support, free in your local authority area [10]. You can ask a service to explain its confidentiality and safeguarding arrangements first, or ask anonymously through FRANK [10].

Clinical review pending

References

1. NHS. Drug addiction: getting help. NHS. https://www.nhs.uk/live-well/addiction-support/drug-addiction-getting-help/
2. NHS. Addiction: what is it? NHS. https://www.nhs.uk/live-well/addiction-support/addiction-what-is-it/
3. National Institute for Health and Care Excellence. Drug misuse prevention: targeted interventions. NICE guideline NG64, published 22 February 2017. https://www.nice.org.uk/guidance/ng64/chapter/recommendations
4. National Institute for Health and Care Excellence. Coexisting severe mental illness and substance misuse: community health and social care services. NICE guideline NG58, recommendations, last reviewed 14 August 2024. https://www.nice.org.uk/guidance/ng58/chapter/Recommendations
5. Office for Health Improvement and Disparities. Adult substance misuse treatment statistics 2023 to 2024: report. GOV.UK, 28 November 2024. https://www.gov.uk/government/statistics/substance-misuse-treatment-for-adults-statistics-2023-to-2024/adult-substance-misuse-treatment-statistics-2023-to-2024-report
6. GOV.UK. Widening the availability of naloxone. GOV.UK, published 23 April 2025, updated 12 September 2025. https://www.gov.uk/government/publications/widening-the-availability-of-naloxone/widening-the-availability-of-naloxone
7. NHS. Alcohol misuse: Treatment. NHS. https://www.nhs.uk/conditions/alcohol-misuse/treatment/
8. NHS. Diazepam. NHS medicines information. https://www.nhs.uk/medicines/diazepam/
9. Black C. Review of drugs part two: prevention, treatment and recovery. GOV.UK, published 8 July 2021, updated 2 August 2021. https://www.gov.uk/government/publications/review-of-drugs-phase-two-report/review-of-drugs-part-two-prevention-treatment-and-recovery
10. FRANK. Find support near you. Talk to FRANK. https://www.talktofrank.com/get-help/find-support-near-you