What are the long-term effects of different types of drugs on the body and mind?
Every substance on this page shows up differently in a blood test, but each one was doing the same job before it became a problem. Here is what the evidence says about the long-term effects, and why the substance itself is rarely the whole story.
In short
- Alcohol, cannabis and cocaine bring the most South Africans into treatment.In the SACENDU bulletin for January to June 2025, alcohol was 24% of national admissions, cannabis 37% (up from 33% the year before), and crack or cocaine 3% (SAMRC, SACENDU Research Brief, 2026).
- Long-term use changes the body in specific, documented ways.Drinking above the NHS guideline of 14 units a week raises the risk of liver, heart and cancer harm (NHS), and regular cannabis use is linked to problems with memory and attention (NIDA).
- The substance is rarely the reason someone starts.It is usually the answer to something else: stress, trauma, anxiety or sleeplessness. Treating only the substance leaves that underneath untouched. See why treating both matters.
Concerned about your own use, or somebody else’s? Book a free, confidential call with our team. We reply the same day.
People rarely arrive at treatment because of one bad night. They arrive after months or years in which a substance quietly became the only thing that worked: for sleep, for nerves, for pain, or simply for getting through a Tuesday. This page covers what long-term use of the most common substances does to the body and brain, substance by substance, and what tends to sit underneath it.
Before you stop anything: speak to a doctor first if you
- drink heavily every day
- take benzodiazepines, sleeping tablets or opioid painkillers most days
- have had seizures, hallucinations or severe shakes when you stopped before
Stopping alcohol or sedatives suddenly after heavy, long-term use needs medical supervision. Understanding drug withdrawal symptoms covers what to expect and when home withdrawal is not safe.
How common is each type of drug among people who go into treatment in South Africa?
Alcohol, cannabis and cocaine account for most treatment admissions nationally. In the SACENDU bulletin covering January to June 2025, alcohol was 24% of admissions, cannabis 37% (up from 33% in 2024), and crack or cocaine 3%, a share that has stayed low for several reporting periods running (SAMRC, SACENDU Research Brief, 2026).
202433%
2025 (Jan to Jun)37%
Share of all national treatment admissions where cannabis was the primary substance, South Africa.
Prescription medicines are covered in their own section below. Cape Town’s own numbers look different: specialist treatment centres in the Western Cape that report to SACENDU list tik (methamphetamine) as the leading substance at 30% of admissions, ahead of alcohol (26%) and cannabis (24%), a different pattern from the one this page covers (see what tik is and what it does).
What are the long-term effects of alcohol on the body and brain?
Long-term heavy drinking damages the liver, heart and brain, and raises cancer risk. The NHS advises no more than 14 units of alcohol a week for both men and women, and says drinking regularly above that raises the risk of liver disease, some cancers, heart problems and stroke (NHS).
What are the long-term effects of high-strength cannabis and edibles?
Frequent or heavy cannabis use is linked to problems with memory, attention and learning. Research cited by the US National Institute on Drug Abuse (NIDA) estimates that 22% to 30% of people who use cannabis meet the criteria for cannabis use disorder, with higher THC concentrations tied to a greater chance of that happening (NIDA).
Cannabis is not simply legal in South Africa. The Cannabis for Private Purposes Act, which President Cyril Ramaphosa signed into law on 28 May 2024, regulates the cultivation, possession and use of cannabis by adults in a private setting (the Presidency, gov.za); it does not create an open retail market, and using it in public or supplying it commercially without a licence both remain restricted. Legal availability has also changed what is on offer: edibles and high-THC concentrates are easier to find now than the cannabis of a decade ago, which matters given the link between higher THC and a greater chance of developing a disorder.
What are the long-term effects of cocaine on the heart and mind?
Long-term cocaine use is linked to impaired attention, memory and decision-making, and to a higher risk of stroke and heart damage. NIDA reports that cocaine use is linked with an increased risk of stroke, inflammation of the heart muscle and aortic ruptures, alongside cognitive effects that build up with continued use (NIDA).
Heavy cocaine use, especially in binges, can also bring on paranoia and, at the extreme, psychosis, in which someone loses touch with reality and experiences hallucinations, NIDA notes.
| Depressants | Stimulants |
|---|---|
| What it does to the nervous system | |
| Slows it down | Speeds it up |
| Covered on this page | |
| Alcohol, benzodiazepines, sleeping tablets, GHB | Cocaine, MDMA, methylphenidate |
| Main long-term physical risk | |
| Liver, heart and organ strain | Heart strain and cardiovascular events |
| Main long-term mental health risk | |
| Memory and cognitive decline | Anxiety, paranoia and, in heavy use, psychosis |
| Stopping after heavy, long-term use | |
| Can be medically dangerous without supervision | A crash in energy and mood; take a sharp drop in mood seriously |
A general pattern, not a diagnosis: opioid painkillers and cannabis sit closer to the depressant side, and are covered in their own sections.
What happens when prescription medicines like benzodiazepines, sleeping tablets, codeine or tramadol are used long term?
Medicines prescribed for anxiety, sleep or pain can still cause dependence with long-term use. Benzodiazepines and codeine both carry a documented risk of dependence and tolerance after weeks of regular use, sleeping tablets such as zolpidem are meant for short courses only, and stopping any of them abruptly after heavy use needs medical support.
Dependence and tolerance to benzodiazepines such as alprazolam can develop after as little as a few weeks of regular use, and stopping abruptly can be dangerous, according to a clinical reference written for doctors (Patient.info).
Sleeping tablets such as zolpidem are meant for short courses only, usually up to four weeks; the NHS warns that using them for longer raises the risk of becoming dependent on them (NHS).
Codeine, available on prescription and, in low doses, over the counter, follows the same pattern: the body can become used to having it with long-term use, and dependence is possible, the NHS says (NHS). Because of that dependence risk, South Africa limits over-the-counter codeine to 10mg per dose, a maximum of 80mg a day, a five-day course, and one pack per customer (SAHPRA, Consolidated Schedules, August 2025).
What about club drugs like MDMA, ketamine and GHB, or drugs used for work, like methylphenidate and modafinil?
MDMA, taken regularly, is linked to poor sleep, memory and mood problems, and can cause a dangerous rise in body temperature in a hot, crowded club. Ketamine and GHB turn up often in the same settings, and methylphenidate and modafinil turn up more in offices and exam halls, taken to stay sharp rather than to go out.
People who regularly use MDMA report poor sleep, low appetite, confusion, depression, anxiety, paranoia and memory or attention problems, according to NIDA, which also names a dangerously steep rise in body temperature, particularly with heavy physical activity or a warm environment such as a club, as a recognised risk (NIDA).
The long-term picture for ketamine and GHB is less documented in the open literature than for the substances above, and neither is something to manage on your own.
Methylphenidate is sometimes used without a prescription for work or study focus. Misusing prescription stimulants carries real risk: a review of the evidence links misuse to psychosis, heart attack and cardiomyopathy in documented, if uncommon, cases (a review on PMC, National Library of Medicine). Modafinil comes up in the same conversations about staying sharp for work, though the evidence on its own long-term risk is thinner.
Why do people become dependent on one substance rather than another?
Substance choice usually tracks what a person needed relief from. Alcohol and benzodiazepines quiet anxiety, stimulants push through exhaustion or low mood, and opioids blunt physical or emotional pain. Longitudinal research links trauma symptoms to later problem drinking more often than the reverse, which is why treatment has to reach what sits underneath the use as well as the substance.
A 2020 review in the Journal of Traumatic Stress, drawing on longitudinal studies, found that post-traumatic stress symptoms typically appear before problem drinking starts: evidence for what clinicians call the self-medication pattern (PMC, National Library of Medicine).
Someone using alcohol to fall asleep and someone using cocaine to get through a deadline can be solving the same underlying problem in opposite directions: different substance, same job.
Treating the substance without treating what sits underneath tends to end in relapse, because the symptoms the substance was managing come back once it is gone. Our page on why dual diagnosis treatment matters covers that pattern and what integrated treatment looks like in practice.
Why is long-term substance use so hard to stop through willpower alone?
Repeated heavy use changes how the brain’s reward system responds to the substance and to everyday pleasures, which is why craving and relapse are so common even when someone genuinely wants to stop. This pattern lives in the body and nervous system and says nothing about character. It is one reason structured, supervised treatment tends to work better than stopping alone.
Tolerance builds the same way for most of the substances on this page: the same dose stops doing what it used to, more is needed to get there, and the gap between doses becomes its own source of discomfort. Deciding to stop is the start; breaking that cycle usually takes clinical help.
How does Renewed Life Center treat someone affected by more than one of these substances?
Renewed Life Center, a private residential rehab in Lakeside, Cape Town, treats the substance and what sits underneath it in one place, following one plan, rather than sending clients between separate services. Medical detox is provided where clinically indicated, with 24-hour nursing supervision, and medication is used only when clinically indicated and prescribed by a medical professional.
One plan matters here because so many people arrive using more than one substance, alcohol alongside a sleep medication, say, or cocaine alongside cannabis, and treating one without the other leaves an obvious gap.
What a stay covers
- A clinical pre-admission assessment within three days of the first call.
- Medical detox with 24-hour nursing supervision, where clinically indicated.
- Medication selected by a psychiatrist where it is needed, and only when prescribed by a medical professional.
- Individual psychotherapy (typically three sessions a week in Phase 1) and group therapy five or more times a week.
- A written relapse-prevention plan built for the home you are actually returning to.
See our drug addiction treatment and alcohol addiction treatment programmes for how we run each, or read what a day in residential treatment looks like.
Book a free, confidential call: 20 to 40 minutes by WhatsApp, video or phone, with no obligation. Admission can be immediate and typically happens within three days of first contact.
What else do people ask?
Not in the way “legal” usually means. The Cannabis for Private Purposes Act allows adults to grow, keep and use cannabis privately, but it does not create an open retail market, and selling it commercially without a licence, or using it in public, both remain restricted (the Presidency, gov.za, 2024).
Yes, and it is common rather than unusual. Alcohol alongside a sleep medication, or cannabis alongside cocaine, are typical combinations, and treatment that only addresses one of them tends to leave a gap the other one fills.
No, but the risk rises with how much and how often someone drinks. The NHS guideline is 14 units a week, and the further and longer someone drinks above it, the higher the risks.
It varies by medicine and by person. Dependence and tolerance to benzodiazepines can begin after only a few weeks of regular use, and sleeping tablets such as zolpidem carry a rising risk of dependence past four weeks, which is why both are meant to be used short term and under medical review.
This article is general information, not medical advice.
Sources
- SAMRC: SACENDU Research Brief, Vol. 29(1) (2026), data for January to June 2025
- NHS: The risks of drinking too much
- NIDA: Cannabis (Marijuana) research topic
- The Presidency, gov.za: media statement on the Cannabis for Private Purposes Act (28 May 2024)
- NIDA: Cocaine research topic
- Patient.info: Benzodiazepine dependence (clinical reference for doctors)
- NHS: Common questions about zolpidem
- NHS: Codeine
- SAHPRA: Consolidated Schedules (1 August 2025)
- NIDA: MDMA (Ecstasy/Molly) research topic
- National Library of Medicine (PMC): review of prescription stimulant misuse
- National Library of Medicine (PMC): 2020 review, Journal of Traumatic Stress, on PTSD and alcohol use disorder
Recognise more than one of these? Talk to us before choosing where to start.
A free first conversation, a clinical assessment within three days, and one plan that treats the substance and what sits underneath it, in one place.
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