| How drugs affect your mental health is a relatively straight forward question to answer. The mood lift, the comedown, the days that feel heavier than they should, the things that get sharper and the things that go quiet are all things that run through the same parts of the brain. Understanding how drugs affect your mental health is therefore a matter of identifying what those parts of the brain do, and what happens when you demand more of them than they can handle. |
How drugs affect your mental health?
Drugs change how you feel because they act on the same brain systems that regulate mood and motivation. The chemicals involved are mostly dopamine, serotonin, and a calming chemical called ‘GABA’. When a drug makes one of these systems work harder than normal, you feel the effect of that push. When the effect wears off, you feel the dip on the other side.
With repeated use, your brain begins to expect the drug, so it makes less of the chemical itself (or becomes less responsive to it). The same mechanism that produces the high now runs in reverse. The reward system is going from either extreme of the scale – enhanced to depleted – with chronic use.
The mental health effects of drug use are this same biological change, showing up in how you think and feel. According to the NHS Adult Psychiatric Morbidity Survey, 10.5% of adults with a common mental health condition show signs of drug dependence, compared with 3.7% of adults without one.
The short-term psychological effects of drugs
The psychological effects of drugs in the short term are what most people notice first. They can show up within hours of using, and last for hours or days afterwards. The pattern varies by substance, but common effects include:
- A mood lift while the drug is active, then a low mood after
- Anxiety, restlessness, or panic in the hours after using
- Disrupted sleep, including trouble falling asleep or staying asleep
- Irritability or a short temper for a day or two afterwards
- Paranoia or feeling watched, especially with stimulants and cannabis
- Trouble concentrating or remembering things the next day
These effects happen because the drug has pushed your brain chemistry in one direction, and once it wears off, your brain is briefly short of what it just used. Some drugs work by mimicking natural brain chemicals, while others cause the brain to release abnormally large amounts of them. Normal communication between brain cells is disrupted for a period afterwards.
The long-term effects of drugs on mental health
When drug use is regular and continues over months or years, the brain’s adjustments stop being temporary. The effects of drugs on mental health at this stage tend to look less like the comedown from a single session and more like an entirely shifted baseline.
What people often notice is:
- A persistent low mood between periods of use
- Anxiety that doesn’t lift the way it used to
- Changes in memory and concentration
- A loss of motivation for things that used to feel worth doing.
- Sleep staying disrupted
- Emotional regulation becoming harder.
The line between how drugs affect your mental health begins to get blurry here. It’s been reported that about half of people who experience a mental health challenge during their lives will also experience a substance use condition, and vice versa. Drug use that comes before the first symptoms of a mental health condition can produce changes in the brain that bring out an underlying tendency towards that mental health challenge.
“I contacted Castle Health with a view to getting online support after a period in rehab. They recommended recovery coaching and arranged for me to meet my coach in person as the first of 10 meetings. I continued the coaching on Zoom as I live in France. I was very happy with my 10 sessions and feel I am in a good place to continue my recovery.”
How different drugs affect mental health
The mental health effect of a drug depends on what it does to your brain chemistry. Stimulants, depressants, and hallucinogens each act on different systems – so the experience of using them and of coming off them looks different.
Cannabis and mental health
Cannabis acts on the brain’s cannabinoid system. That system shapes mood and perception. In the short term, the effects most often reported are anxiety and a sense of disconnection, sometimes tipping into paranoia. With regular use, motivation and short-term memory often dip noticeably.
The link with serious mental illness matters most for people who already have a family history of psychotic illness, or who started using young. According to Manchester University NHS Foundation Trust, you are more likely to develop a psychotic illness if you smoke cannabis, although it is rarely the only cause.
Cocaine and mental health
Cocaine floods the brain with dopamine, the chemical involved in motivation and reward. That’s the ‘high’. The comedown afterwards is your brain briefly short of the dopamine it just used.
That shortage is why low mood and irritability follow in the days after use. Research published in The Primary Care Companion for CNS Disorders notes that cocaine can produce a wide range of psychiatric symptoms, and that mental health conditions already present tend to get worse with continued use.
With repeated use, the dopamine system becomes less responsive overall. People often notice depressive episodes between periods of use, persistent anxiety or panic, and paranoia. Memory and concentration can be affected while the brain rebalances.
Our page on cocaine addiction covers what dependence looks like and what treatment options exist.
MDMA, ecstasy and other stimulants
MDMA and ecstasy work mainly by releasing a large amount of serotonin, the chemical that influences mood and sleep. The release is what produces the lifted mood and connection people describe. The dip afterwards, sometimes called the midweek low, is your brain temporarily short of serotonin. American Addiction Centers, an American treatment provider, describes effects lasting for days afterwards: low mood, irritability, and trouble concentrating.
Amphetamines and methamphetamine act on the same systems more aggressively. Regular use can produce persistent anxiety and sleep problems, and the comedowns tend to be heavier.
Heroin and other opioids
Opioids slow down the body and produce a deep sense of calm or sedation. With regular use, that calm starts to flatten into something more like emotional blunting, where the highs are gone and the lows are harder to lift out of. Depression and anxiety are common, both during use and withdrawal.
Research found that psychiatric symptoms are very common among people seeking treatment for opioid dependence, with about 46% experiencing a major depressive episode alongside their opioid use.
Hallucinogens and psychedelics
LSD, magic mushrooms, ketamine, and DMT change perception by acting on serotonin or other receptors in unusual ways. For most people, the effect ends with the experience. For some, perceptual changes can persist after the drug has worn off, a pattern sometimes called Hallucinogen Persisting Perception Disorder.
A study in Drug and Alcohol Dependence Reports found past hallucinogen use was linked with higher rates of depression, PTSD, ADHD, and anxiety.
Ketamine specifically is associated with the feeling of being detached from yourself or your surroundings (called ‘dissociation’) which can persist for some users between sessions.
Other substances worth knowing about
Inhalants, mephedrone, GHB, and the substances often grouped as ‘legal highs’ each act differently, and the research on their mental health effects is less complete. Most of them produce a short-term high followed by a comedown that involves low mood, anxiety, or sleep disruption. Repeated use of any of them can affect mood and cognition in the longer term.
When drug use and mental health start to feed each other
There’s a point where it becomes hard to tell which came first. Are you using drugs because of how you feel, or feeling this way because of how you’re using? For many people, the two start to drive each other.
This pattern of how drugs affect your mental health in a loop is common. The NHS Adult Psychiatric Morbidity Survey found that 10.5% of adults with a common mental health condition show signs of drug dependence, almost three times the rate seen in adults without one.
When both are present at the same time, the clinical name is dual diagnosis, and treating one without the other rarely works well. Our page on when drug use and mental health overlap goes into what dual diagnosis treatment actually involves.
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When to seek help with drug use and mental health
There isn’t a single moment that marks when drug use has tipped into something worth talking to someone about. But there are signs that things have moved past curiosity, and into territory where outside help would make things easier. These signs include:
- Mental health symptoms that persist between periods of use, not just after
- Using drugs to manage how you feel, rather than for pleasure or to socialise
- People in your life noticing changes in your mood or behaviour
- Wanting to cut down or stop, and finding it harder than you expected
- Using more often, or more heavily, than you used to
- Feeling mentally worse on the days you don’t use
None of these on their own means you have an addiction. But several of them together, especially over time, are worth taking seriously.
How to get help
There are a few places you can start, and the right one depends on what you need.
- Your GP is a good starting point, particularly if you want to talk through both the mental health and the drug use side at once. They can refer on to NHS drug and alcohol services in your area.
- NHS drug services are free and confidential, available across the UK. The NHS website has a service finder for your postcode.
- Samaritans – if things feel urgent and you need to talk to someone now, you can call them on 116 123, any time.
If you’re considering private treatment, you can find out more about what inpatient treatment involves, and our outpatient treatment pages cover the options for people who want to stay in their own routine while getting support. Our treatment for drug addiction page brings the whole pathway together.
You don’t need to know which one is right before you make contact. Working out what suits you is part of what an initial conversation is for.
If someone you know is using drugs
If someone in your life – rather than yourself – is using drugs, the experience you’re having can feel challenging. Some people might feel worried, guilty about not having noticed sooner, frustrated that conversations don’t go the way you hoped, or helpless when nothing you say seems to land. None of it means you’re handling it badly.
- What helps most is approaching the conversation when no one is in crisis.
- Calm and specific tends to land better than emotional and broad.
- Tell them what you’ve noticed rather than what you think it means.
- Ask, rather than tell.
The aim of the first conversation is to make the next one possible.
Addiction affects more than the individual living with the condition. At Castle Health, family therapy is part of what we offer, because we know that the people around someone in recovery often need their own space to make sense of what’s happened and what comes next.
- 10.5 of adults with a common mental health condition show signs of drug dependence, compared with 3.7% of adults without one (Source: NHS Adult Psychiatric Morbidity Survey, England 2023–24.)
Frequently asked questions about how drugs affect mental health
Can mental health changes from drug use be reversed?
Often, yes, although not always completely. Many short-term effects ease within weeks of stopping, as the brain rebalances. According to a clinical review held by the US National Library of Medicine, some drugs can leave changes that persist longer, particularly with heavy or prolonged use. Mental health symptoms that were present before the drug use started are less likely to clear just by stopping, and usually need their own treatment.
Why do I feel worse mentally when I stop using drugs?
This is the rebound effect. Your brain is recalibrating after being pushed toward either extreme level. The chemicals that the drug was pushing need time to settle. For most substances that takes days to a few weeks, although it can be longer with heavy use. It tends to be hardest in the first stretch, and easier from there.
Is it possible to use drugs occasionally without affecting my mental health?
This depends on the substance, how often, your age, and whether anyone in your family has a history of mental illness. Some people use occasionally for years without obvious mental health effects. Others find that even infrequent use leaves them feeling low for days, or kicks off anxiety they don’t have otherwise. There isn’t a safe dose for everyone. The most useful gauge you have is how you actually feel in the days after using.
