Substance abuse can take many forms, with the 'substances' in question including alcohol, cannabis, heroin, solvents, ecstasy, amphetamines, LSD, cocaine, crack cocaine, anabolic steriods, cigarettes and a range of medications such as benzodiazepines, pain-killers and stimulants.
What these all have in common, however, is that their abuse is not in the best interests of the individual - with a broad range of adverse consequences including ill health, long-term mental illness (eg. schizophrenia), dependency, psychosis, cancers and death. Additional consequences are the effects of possible contaminants that may be contained within the drug, potential infections associated with injection (eg. HIV, Hepatitis C etc), involvement in crime, withdrawal from other activities (eg. school, university, work, relationships, family life), trouble with the police, and wasting a lot of money repeatedly purchasing the substance.
