What are the long-term effects of drug and substance abuse on the body and mind?

It also raises the risk of depression, anxiety and psychosis.

Nationally, cannabis was 37% of treatment admissions in South Africa in January to June 2025 and alcohol 24%, SACENDU found. In the Western Cape over the same months, tik led at 30%. The first signs are usually small: a son who sleeps through the day, a husband who is calm one night and snappy the next.

What do drugs do to you? How substance abuse changes the brain

Drugs hijack the chemical messengers brain cells use to talk to each other, and repeated use rewires the reward system, NIDA explains. Some, such as heroin, mimic those messengers; others, such as cocaine and tik, flood the brain with its own chemicals.

Either way, dopamine surges far above anything food or company produce, and dopamine teaches the brain to repeat whatever caused it. Over months the brain makes fewer of its own reward chemicals, so ordinary life feels flat without the drug. Addiction is that change. It can be treated, usually by treating what the drug was covering as well.

How does substance abuse impact an individual’s physical health?

The physical consequences of substance abuse reach almost every organ: NIDA lists lung and heart disease, stroke, cancer and mental health conditions among the problems that come with addiction.

Nine lifestyle diseases caused by substance abuse

1. Liver disease, up to cirrhosis.
2. Heart disease: alcohol caused an estimated 474,000 cardiovascular deaths in 2019, the WHO reports.
3. Stroke, linked to heavy drinking and cocaine.
4. Cancer, including breast and liver cancer.
5. Lung disease.
6. HIV: injecting drugs accounts for 1 in 10 HIV cases, according to NIDA.
7. Hepatitis C, spread by shared needles.
8. Tuberculosis, which the WHO counts among the diseases alcohol causes.
9. Depression and anxiety.

Types of drugs and the long-term effects of substance abuse

The effects of drug abuse differ by drug. Below are the ones that most often bring people into treatment in South Africa.

Alcohol: long-term effects on the body and brain

Years of heavy drinking damage the liver, heart and brain. Alcohol plays a causal role in more than 200 diseases and injuries and caused about 2.6 million deaths worldwide in 2019 (WHO).

Cannabis (weed or marijuana), high-THC strains and edibles

Heavy cannabis use is linked to problems with memory, attention and learning. Research cited by NIDA estimates that 22% to 30% of people who use cannabis meet the criteria for cannabis use disorder, and higher THC is linked to a greater chance of it. In South Africa the Cannabis for Private Purposes Act of 2024 covers private use by adults only.

Cocaine and crack: side effects on the heart, nose and mind

Long-term cocaine use is linked to stroke, inflammation of the heart muscle and worse memory and decision-making, according to NIDA. Snorting it regularly can cause nosebleeds and a lost sense of smell, and binges can bring on paranoia. Mixed with alcohol, cocaine forms cocaethylene, which may add to the toxic effect on the heart.

Tik (crystal meth, methamphetamine)

NIDA lists the long-term effects of tik as anxiety, insomnia, mood swings, psychosis with hallucinations and tooth loss known as “meth mouth”. In the Western Cape it is the most common reason people enter treatment. Our guide to what tik is and what it does has more.

Heroin, nyaope and whoonga

Nyaope and whoonga are street names for heroin, often mixed with other substances, SACENDU notes; in South Africa nyaope is usually sprinkled on cannabis or tobacco and smoked. Opioids are highly addictive. A South African Journal of Science article on whoonga lists damaged and infected veins, damaged heart valves, liver failure, kidney disease and lung problems among the harms. Mixed with alcohol or sedatives, opioids can slow breathing until it stops: the official drug label warns of profound sedation, respiratory depression, coma and death. Our page on heroin withdrawal covers what stopping involves.

Mandrax and white pipe

Mandrax (methaqualone) is a sedative, smoked mostly as “white pipe” with cannabis. Cannabis with mandrax made up 6% of primary admissions in the Western Cape in the first half of 2025, the highest of any region, SACENDU found. Like other sedatives, it is not something to stop alone after daily use.

Benzodiazepines, sleeping tablets, codeine, tramadol and lean

Medicines for anxiety, sleep or pain can still cause dependence. With benzodiazepines such as alprazolam it can develop after a few weeks of regular use, according to a clinical reference for doctors, and the FDA warns that stopping them abruptly can bring on seizures. Sleeping tablets such as zolpidem are meant for short courses, usually up to four weeks, the NHS says.

Codeine and tramadol are opioids, and codeine carries a risk of tolerance and eventually dependence, SAHPRA notes. South Africa limits codeine sold over the counter to 10mg per dose, 80mg a day, a five-day course and one pack per customer, under SAHPRA’s schedules of August 2025. Recreational use of codeine cough syrups is widely described, and a 2026 Business Day report says the use of lean in South Africa has reached “epidemic” levels.

MDMA, GHB and work drugs like Ritalin, Adderall and modafinil

Regular MDMA use brings poor sleep, depression, anxiety and memory problems, NIDA notes. GHB dependence can develop quickly, the NHS warns, and after more than seven days in a row it should not be stopped alone: coming off it is a tapered process under medical supervision. Ritalin, Adderall and modafinil turn up in offices and exam halls; a review in the US National Library of Medicine links stimulant misuse to psychosis and heart attack.

What are the mental and emotional effects of substance abuse?

Long-term substance abuse effects on the mind include depression, anxiety and, with stimulants and high-THC cannabis, paranoia and psychosis. The link runs both ways: 35% of US adults with a mental disorder also have a substance use disorder, NIDA reports.

Among the negative effects of substance abuse, people feel the comedown first, and the more often it repeats, the more that low mood blurs into depression. Most drugs also break sleep, which makes mood worse again.

Sometimes the problem came first. Alcohol is often used to cope with the symptoms of mental health conditions, even though it ends up making them worse, NIAAA notes, and a 2020 review in the Journal of Traumatic Stress found that post-traumatic stress symptoms typically appear before problem drinking starts.

Take the substance away and leave the reason, and the reason sends you back. NIDA advises treating mental health conditions and addiction at the same time, and that is how our programme is built. Ruby Weber, our psychologist, leads the psychological side of our dual diagnosis work; she has more than twenty years in the addictions field with South African and international clients.

What are the dangers of substance abuse as a risky behaviour?

Substance abuse counts as a risky behaviour because it dims the part of the brain that weighs consequences and turns up the drive for reward. Three potential dangers of substance abuse stand out:

• Injuries, including road crashes, which the WHO lists among the harms caused by alcohol.
• Infections: unplanned sex and shared needles spread HIV and hepatitis C.
• Overdose from mixing opioids with alcohol or sedatives.

After that come arrests, debt and lost jobs. The dangers of using drugs feed themselves: shame afterwards is one of the strongest pulls back to using.

What is the negative impact of substance abuse on family, work and relationships?

The disadvantages of substance abuse, and the negative impact of drugs on a family, often show at home before anyone names them. A mother sees her daughter’s wide pupils and hears her talk too fast. A wife finds the bottle behind the washing powder. A manager sees Monday sick days pile up.

Each sign alone is easy to explain away, but together they make a pattern. Trust is usually the first of the consequences of drug abuse to go. The list in signs of drug dependency helps you see where things stand.

If you want to raise it, pick a calm moment when they are sober, talk about specific things you have seen and how they affect you, and leave out labels and threats you will not carry out. If they drink or take pills every day, do not push them to stop overnight or pour everything away, because stopping suddenly can be dangerous; the safer next step is a plan with a medical team.

You do not have to wait until the person is ready before you get help. A relative can talk to our team before the person has agreed to come: about what you have noticed and what treatment would involve. Once someone is in treatment with us, families join a group by video every week.

Overdose and medical emergencies: what are the warning signs?

Overdose is the most serious danger of drug abuse, and it can happen the first time, especially when substances are mixed. The WHO describes opioid overdose by pinpoint pupils, unconsciousness and difficulty breathing, and counts about 125,000 opioid overdose deaths worldwide in 2019 (WHO).

Other signs include seizures, chest pain, blue lips, or someone you cannot wake. An overdose is a medical emergency: get emergency help now rather than waiting for a reply from us. Stay with the person, and if they are unconscious but breathing, lay them on their side so the airway stays open.

Stopping can be dangerous too. If you drink every day or take opioids, benzodiazepines, mandrax, GHB, codeine or sleeping tablets daily, or had seizures or severe shakes the last time you stopped, do not stop suddenly on your own. Write to us before you stop: after an assessment, our medical team decides whether you need a supervised detox and runs it if you do. Our guide to drug withdrawal symptoms explains what to expect.

How does short-term use turn into long-term dependence?

Short-term use turns into long-term dependence through tolerance: the brain adapts to each dose, so the same amount stops working and you need more. The drug also gets tied to moments, such as sleep at night, which is why willpower alone so often fails. It usually shows up in questions like these:

• Do you use more, or for longer, than you planned?
• Have you tried to cut down and found you could not?
• Do you feel ill, flat or on edge when you go without?

If you recognise yourself in them, tell us what has made cutting down hard; that is what the first conversation is for, and you do not need to be sure it is serious first. If it is alcohol or pills every day, or you mix, do not stop suddenly on your own: talk to us before you try. The same goes for a low mood after stopping cocaine or tik that is heavy or will not lift: write to us rather than sit it out alone.

If that low mood comes with thoughts of suicide, talk to a professional about it now rather than waiting for it to pass. If you might harm yourself now or cannot keep yourself safe, get emergency help immediately rather than waiting for a reply from us; the SADAG Suicide Crisis Helpline is 0800 567 567. When you are safe, you or someone close to you can talk to us about treatment: the low mood and the drug are worked on together, with your own counsellor every week and a psychologist who heads that side of the work.

Recognise the pattern at home, or in yourself? Tell us what you have noticed.Recognise the pattern at home, or in yourself? Call +27 79 880 0045, free and confidential.

Substance use and abuse in South Africa: which drugs bring people into treatment?

Cannabis, alcohol and tik account for most treatment admissions.

202433%

2025 (Jan to Jun)37%

In the Western Cape the order is different: in January to June 2025 tik led at 30%, ahead of alcohol (26%) and cannabis (24%). Mixing is the norm here: SACENDU found that in the second half of 2025, 63% of people in treatment in the province used more than one substance. Alcohol with sleeping tablets, or cocaine with cannabis, needs one plan for both.

Reaching out for help: how is long-term substance abuse treated?

Substance abuse treatment works best when the drug and the reason for it are treated together, and it takes time: NIDA’s Principles of Drug Addiction Treatment note that remaining in treatment for an adequate period of time is critical.

That is how Renewed Life Center in Lakeside, Cape Town, works. Therapy uses CBT and DBT for the urges behind using, schema therapy for old patterns, and EMDR, which NICE recommends for post-traumatic stress. There are 12-step meetings in the evenings, and family therapy brings in the people at home.

Nikki Edwards leads the programme as Programme Director and Clinical Manager, and John Roberts, Senior Recovery Specialist and Operations Manager, usually takes the first call; with 11 and 39 years of recovery, both also know addiction from the inside. Leila Bolland, social worker and therapist, has done this work since 2015. Dr John Wulz, our GP, has a background in mental health and emergency medicine. He examines you after you arrive and reviews any medication you already take; if you need a medical detox, our medical team runs it.

Admission can be immediate and typically happens within three days of first contact. The fee depends on the programme and how long you stay; you hear it on the first call and get it in writing the same day. See our drug addiction treatment programme, or tell us on WhatsApp what is going on and we will say how soon you can start.

What else do people ask?

What is substance abuse? Examples of substance abuse

Substance abuse is using alcohol, drugs or medicines in a way that harms your health, work or relationships. Examples: drinking every night to get to sleep, taking someone else’s sleeping tablets, smoking cannabis daily, using cocaine at weekends, or mixing pills with drink.

What are the long and short-term consequences of substance abuse?

Short term: impaired judgement, injuries and road crashes, a comedown and overdose. Long term: liver, heart and lung disease, stroke, cancer, HIV and hepatitis C, depression, psychosis and dependence. The consequences of substance abuse grow with how long and how heavily someone uses.

What do drugs do to your body?

Drugs change how brain cells send and receive signals, NIDA explains, and the body follows: opioids, for example, shrink the pupils and slow breathing, the WHO notes. Over years the damage reaches the liver, heart, lungs and brain, as the sections above show.

Compare the long-term effects of marijuana and alcohol abuse

For alcohol the WHO counts more than 200 diseases and injuries, including heart disease and several cancers, as well as depression and anxiety, and stopping after heavy daily drinking can be dangerous. Heavy cannabis use is linked to problems with memory, attention and learning, and higher THC to a greater chance of cannabis use disorder, NIDA notes.

Critically discuss two long-term impacts of substance abuse

First, physical: heavy drinking moves the liver from fatty liver to cirrhosis so silently that people keep drinking long after the damage starts. Second, mental: repeated use changes the reward system, so ordinary life feels flat without the drug, which keeps dependence going. Both improve when the reason for using is treated along with the substance.

When should I worry about someone after they have used?

If breathing is slow or has stopped, lips turn blue, they cannot be woken, or there is a seizure or chest pain, call local emergency services immediately. Do not wait for a WhatsApp reply. If you are worried about the pattern rather than one night, message us on WhatsApp: we reply the same day and can talk it through with you.