Drugs, alcohol and addiction

The commonly abused drugs are opioids, cannabinoids and coca alkaloids, mostly from flowering plants and some from fungi. Opioids bind opioid receptors in the central nervous system and gastrointestinal tract.

Heroin (smack) is diacetylmorphine, a white, odourless, bitter crystalline compound made by acetylating morphine, which comes from the latex of the poppy Papaver somniferum. Usually snorted or injected, heroin is a depressant that slows body functions. Morphine itself is a very effective sedative and painkiller, useful after surgery.

Cannabinoids act on cannabinoid receptors, mainly in the brain. They come from the inflorescences of Cannabis sativa; its flower tops, leaves and resin give marijuana, hashish, charas and ganja, taken by inhalation or orally, with effects on the cardiovascular system. Some sportspersons abuse them.

Cocaine (coke, crack), from the coca plant Erythroxylum coca of South America, interferes with the transport of the neurotransmitter dopamine. Usually snorted, it strongly stimulates the CNS, giving euphoria and more energy; excessive doses cause hallucinations. Atropa belladona and Datura are other hallucinogenic plants.

Medicines for depression and insomnia, such as barbiturates, amphetamines and benzodiazepines, are often abused. Use of any drug for a non-medicinal purpose, or in amounts or frequency that impair physical, physiological or psychological functions, is drug abuse.

Tobacco, used for more than 400 years, is smoked, chewed or taken as snuff. Its alkaloid nicotine makes the adrenal gland release adrenaline and nor-adrenaline, which raise blood pressure and heart rate. Smoking raises the risk of lung, throat and urinary bladder cancer, of bronchitis and emphysema, of coronary heart disease and of gastric ulcer; chewing raises the risk of oral cancer. Smoking also raises CO in blood and lowers haem-bound oxygen.

Adolescence, roughly 12-18 years, is a vulnerable bridge between childhood and adulthood. Curiosity, adventure and experimentation, exam stress, the idea that drugs are 'cool' (helped by media), unstable families and peer pressure push the young towards drugs and alcohol.

Addiction is a psychological attachment to effects such as euphoria. Repeated use raises the tolerance of the body's receptors, so only higher doses work, and even one use can lead to addiction. Dependence is the body's unpleasant withdrawal syndrome (anxiety, shakiness, nausea, sweating) when regular use stops abruptly; it can be life-threatening.

Effects: reckless behaviour, vandalism and violence; overdose can cause coma and death by respiratory failure, heart failure or cerebral haemorrhage; sharing needles spreads AIDS and hepatitis B; chronic use damages the nervous system and liver (cirrhosis); use in pregnancy harms the foetus. Anabolic steroids misused in sport cause masculinisation in females, testis shrinkage and reduced sperm in males, and in adolescents premature closure of long-bone growth centres, stunting growth.

Preventing abuse beats treating it: avoid undue peer pressure, educate and counsel, seek help from parents and peers, watch for danger signs, and seek professional and medical help. Parenting that combines high nurturance with consistent discipline lowers the risk of abuse.