Substance abuse is characterized by a pattern of use that causes significant impairment or distress, in addition to any one of these additional diagnostic criteria: using substances in situations where it endangers the user; a failure to fulfill major obligations at work, school or home; having multiple drug-related legal problems; or continuing to use substances regardless of the problems it causes in the user's life. The different types of substance abuse have various features depending on the type of drug abused.
Stimulants include illegal drugs such as cocaine and methamphetamine, as well as legal substances such as nicotine, caffeine and over-the-counter stimulants. According to Darryl S. Inaba and William E. Cohen, authors of "Uppers, Downers, All-Arounders: Physical and Mental Effects of Psychoactive Drugs," stimulant use causes the release of the neurotransmitters dopamine and norepinephrine, stimulating the brain's reward and pleasure center. This stimulation reinforces the drugs' abuse, as users attempt to feel good through increases of dopamine and norepinephrine and to avoid the "crash," medically known as dysphoria, that occurs after stimulant use depletes the levels of these neurotransmitters in the brain. Abuse of stimulants depletes energy and creates intense drug cravings and withdrawal symptoms. It can also induce paranoia, irritability, restlessness, insomnia, aggression, violence and psychosis. Stimulant abuse and addiction develop quickly.
Depressants include opiates such as heroin, morphine and opium, as well as sedative-hypnotic medications such as Xanax, Ativan and Valium. Depressants slow down the central nervous system, diminish inhibitions, create relaxation and decrease pain. Opiate abuse carries a high risk of overdose and addiction, as well as health problems. Abuse of sedative-hypnotic drugs easily creates psychological and physical dependence as well. Abuse of these drugs in combination with alcohol can be lethal. Indeed, multiple drug abuse is common with abusers of this class of drug, as users combine various depressants throughout a day or week to try to achieve an optimal psychological and physiological state, notes "Uppers, Downers, All-Arounders."
Psychedelic abuse includes using indole psychedelics such as LSD and psilocybin mushrooms; phenylalkylamine psychedelics including mescaline; and other types of psychedelics such as ketamine, or "Special K," and PCP, notes "Uppers, Downers, All-Arounders." (MDMA, or ecstasy, acts both as a psychedelic and as a stimulant, according to the National Institute on Drug Abuse.) Psychedelics, called hallucinogens in the medical literature, distort the user's perceptions, thoughts and sensations. Abusers who have underlying mental health issues face particular risks as these substances can trigger latent mental health problems.
These drugs vary dramatically in potency. Because they are less well researched than other substances, the effects of abuse are less well known. MDMA abuse may cause lasting damage to the serotonin-producing neurons in the brain, in addition to depression and serious health risks. Ketamine abuse can lead to convulsions and coma. LSD abuse causes such impaired judgment and reasoning that serious injury and death can result even at low doses. Acute anxiety reactions can also occur.
The most commonly abused illegal drug, marijuana induces short-term euphoria, physical relaxation, distorted perception and thought, increased appetite, and impairment of memory and physical coordination. According to the National Institute on Drug Abuse, users of more potent marijuana may experience giddiness, illusions and hallucinations. Because of the impairment in coordination and thinking, driving and other activities while under the influence pose a risk. Tolerance quickly develops so that those abusing marijuana need higher doses to achieve the same high. Long-term marijuana abuse may cause respiratory problems and immune system suppression. According to Inaba and Cohen, longer-term abuse may also stunt emotional maturity and learning, and it can increase anxiety and even cause temporary psychosis.
Alcohol affects every organ in the body, and it is the oldest and most widely used psychoactive substance, notes the National Institute on Drug Abuse. Alcohol abuse includes binge drinking and other problematic patterns of drinking which fall short of addiction but meet the criteria for abuse. Alcohol abuse is linked to increases in aggression, impaired judgment, diminished inhibitions, mood problems such as depression and anxiety, health problems, sexual dysfunction and relationship problems. Alcohol abuse differs from alcoholism primarily in the lack of withdrawal symptoms when an alcohol abuser stops drinking. However, alcohol abuse creates significant distress or impairment in the abuser's life.