Mental health

Find information about drugs and alcohol and mental health.

The relationship between mental health and drug and alcohol use is complex because one can affect the other.

Alcohol and other drugs affect chemicals in the brain responsible for regulating feelings and social behaviour. Alcohol and other drugs can deplete or change the levels of these chemicals, causing short- and long-term impacts on mental health concerns.

Everyone is different but for most people their first experience of mental health problems will arise early in life. Teens are particularly vulnerable to developing mental health problems, because adolescence is a period where organising, construction and strengthening of connections in the brain is happening.

Some of the effects of drug and alcohol use on mental health may include:

  • feeling down or unmotivated to do anything
  • withdrawing from friends and family
  • becoming irritable, angry or aggressive
  • changes in sleeping patterns
  • skipping school or work
  • taking more risks than usual.

Young people who already experience mental health problems, or who have a family history of mental health problems, are more sensitive to the effects of alcohol and other drugs. Substance use can trigger mental health problems such as depression, anxiety, or psychosis (unusual thoughts, hearing or seeing things that are not there) or make their mental health symptoms worse. 

Find out more on the Your Room page Young people and alcohol & other drugs – scroll down to the mental health section.

It has been suggested both that mental illness can cause drug problems (when a person takes drugs in the hope of escaping their symptoms), and that heavy drug use over time causes mental health problems. Most of the evidence, however, seems to indicate that the same factors can lead to both types of problems; that is, biological, social and/or environmental factors predispose a person to have both a mental health and a substance abuse problem.

Both drug and alcohol and mental health services have become much more aware of this situation, and best practice in both areas is now to treat both disorders if this is appropriate. If you are choosing a drug and alcohol treatment program for a friend or relative, it is important to ask whether they will help with any mental health problems.

If the client is a polydrug user, it is also important that the agency can treat each type of drug.

Polydrug use means

  • using two or more drugs in combination (eg tobacco and alcohol)
  • using one drug to counteract the effects (or the after effects) of another
  • using different drugs at different times over a short period of days or weeks.

Polydrug use is very common among people who use drugs. Using a single psychoactive drug can be dangerous; using more than one significantly increases the risks. In particular, if two drugs of the same type, such as the depressants heroin and alcohol, are used together, there are greatly increased risks of accidents, overdose and death.

Other common dangerous drug combinations include ecstasy with alcohol, heroin with sedatives, and amphetamines with sedatives. Because alcohol is the most widely abused psychoactive drug, it is also the most commonly involved in risky polydrug use.

Alcohol and mental health

The relationship between mental health and drug and alcohol use is complex because one can affect the other.

Many people who have alcohol-related problems also have mental health problems. For example, people with post-traumatic stress disorder (such as war veterans and people who have experienced violence) are more likely to develop problems with alcohol.

There are also strong associations between alcohol problems and affective disorders such as major depression, bipolar disorder and anxiety disorders. The use of alcohol can make the symptoms and prognosis of mental illnesses worse.

Can cannabis cause mental health problems?

Cannabis use can have serious consequences for the mental health of particularly vulnerable people. It increases the frequency of episodes of psychosis in those with a disorder such as schizophrenia. Whether it can cause a psychotic illness is not known, but it appears that heavy use at a young age can bring about a psychotic episode in susceptible individuals, and at a younger age.

The association between anxiety and depression is less certain, but there is some evidence that regular, long term cannabis use from an early age may increase the risk of experiencing symptoms into adulthood. Regular adolescent use may also increase the risk of attempting suicide.

Drugs and the developing brain 

Adolescence and emerging adulthood are periods of significant brain growth and development. Scientists call the adolescent brain highly 'neuroplastic' because it is a time of organising, construction and strengthening of connections in the brain.

The Respect Your Brain animated video series explores how alcohol, cannabis, MDMA, alcohol with antidepressants, vaping affect a developing brain.

Prevalence of mental health problems associated with drug use

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