Dependence on a drug can be physical, psychological or both. Many daily drug users demonstrate signs of both.

Cannabis is a generic name for a variety of preparations derived from the plant Cannabis sativa. A sticky resin which covers the flowering tops and upper leaves, most abundantly in the female plant, contains more than 60 cannabinoid substances.

The biological perspective is a way of looking at psychological topics by studying the physical basis for animal and human behavior. It is one of the major perspectives in psychology and involves such things as studying the brain, immune system, nervous system, and genetics.

Drugs are chemicals or substances that change the way our bodies work. When you put them into your body (often by swallowing, inhaling, or injecting them), drugs find their way into your bloodstream and are transported to parts of your body, such as your brain. In the brain, drugs may either intensify or dull your senses, alter your sense of alertness, and sometimes decrease physical pain.

Explore the variety of effects of different types of psychoactive drugs - from stimulants to depressants - on the brain's chemistry and function.

The brain contains many billions of cells, which are joined together at synapes - junctions at which they communicate through one-way signals. These signals are transmitted within the brain and enable actions such as a movement of the arm to happen.

The brain is made up of many parts that all work together as a team. Different parts of the brain are responsible for coordinating and performing specific functions. Drugs can alter important brain areas that are necessary for life-sustaining functions and can drive the compulsive drug abuse that marks addiction.

Drug use, use of drugs for psychotropic rather than medical purposes. Among the most common psychotropic drugs are opiates (opium, morphine, heroin), hallucinogens (LSD, mescaline, psilocybin), barbiturates, cocaine, amphetamines, tranquilizers, and cannabis. Alcohol and tobacco are also sometimes classified as drugs.

The use of drugs for recreational and nonmedical purposes is called drug abuse. The term refers to the use of illegal substances, such as cocaine and marijuana, as well as the use of legitimate drugs—that is, prescription and over-the-counter drugs—in excessive quantities or for nonmedical purposes. Commonly abused substances range from agents such as anabolic steroids, which some athletes use to boost their strength and performance, to psychotropic, or mind-altering, substances that produce changes in mood and feelings.

The term drug abuse is normally applied to excessive and addictive use of drugs. Because such drugs can have severe physiological and psychological, as well as social, effects, many governments regulate their use.

Marijuana is a shredded, green-brown mix of dried flowers, stems, and leaves from the plant Cannabis sativa. A stronger form of marijuana, called hashish (hash), looks like brown or black cakes or balls.

The article examines the possible casual relation between cannabis use and psychotic and affective illness later in life. According to a study the risk of psychos increased roughly 40% in people who used cannabis, and that there is a dose-response effect, leading to an increase risk of 50-200% in the most frequent users.

Marijuana is a crude drug composed of the leaves and flowers of plants in the genus Cannabis.

Studies have suggested that as many as 1 in 4 cannabis users may be genetically at risk for developing schizophrenia or a related psychotic disorder. Now, a new study reveals all users are at risk.

The results demonstrated that ecstasy/polydrug users viewed themselves as being more evening types and having poorer sleep quality than cannabis users and drug naive participants. They were also more likely to have missed a night's sleep. The reported differences in sleep type may reflect ecstasy-related serotonergic dysfunction resulting in problems with shifting circadian rhythms.

Cannabis is the most widely used illicit drug in the world, and regular use has been associated with reduced motivation, i.e. apathy.

Use of crystal methamphetamine, or ice, by drug users in Australia has increased significantly since last year, research shows. Lucy Burns, a senior lecturer at the centre, said this was a worrying pattern because of the serious effects of ice on mental health. "Methamphetamine is associated with psychosis, aggressive behaviour and unpredictability," Dr Burns said.

Amphetamines stimulate the nervous system and are used in the treatment of depression, obesity, attention deficit hyperactivity disorder (ADHD), and narcolepsy, a disorder that causes individuals to fall asleep at inappropriate times during the day. Amphetamines are commonly abused as recreational drugs and are highly addictive.

Amphetamine, prototype of a series of synthetic drugs, all called amphetamines, that have pronounced stimulatory actions on the central nervous system.

Amphetamines are second to cannabis as the most prevalent illicit drug used in Australia, and amphetamine abuse and dependence are associated with significant health and psychosocial harms.

We hear many different things about how alcohol affects the brain and body, most notably that it is a depressant. That’s only part of the story. Alcohol is a depressant, but it’s also an indirect stimulant, and plays a few other roles that might surprise you.

Alcohol abuse and alcohol dependence are often associated with abuse of, or dependence on other substances, including nicotine, marijuana, cocaine, heroin, amphetamines, sedatives, and anxiolytics (anti–anxiety drugs).

An overwhelming desire to drink alcohol, even though it is causing harm, is a disease called alcoholism. Alcohol is a drug. In the United States alcoholism is the most widespread form of drug abuse, affecting at least 5 million persons.

In a simple perceptual discrimination task, even a moderate dose of alcohol decreased the rate of information processing and negatively affected the non-decision component.

Alcohol affects several neurotransmitter systems within the brain. In this article, the author describes its effects on 5 major ones: glutamate, gamma-amino-butyric acid (GABA), dopamine, serotonin, and opioid systems.