Methamphetamine is an odourless, white crystalline powder with a bitter taste. It is soluble in liquid and can be injected, snorted, ingested, or smoked. It is a central nervous system stimulant drug that increases the release of dopamine and leads to high levels of the chemical in the brain. Dopamine is responsible for the pleasure functions of the brain that relate to reward, motivation, the experience of pleasure, and motor function.

The production of excessive dopamine causes an intense rush of pleasure followed by a euphoric high that can last up to twelve hours.The abuse of methamphetamine is associated with a number of negative consequences, which include cognitive dysfunctions and neurological damage. Effects of chronic abuse are depression, psychosis and psycho-motor dysfunctions. Neuropsychological abnormalities include attention deficits, memory problems and poor decision-making.

The use of methamphetamine is associated with long-term biochemical and structural effects on the brain and significantly changes how the brain functions. The excessive production of dopamine causes neuropathological changes in the brain and has a neurotoxic effect on the brain cells that store dopamine and serotonin. These changes include decreases in the levels of dopamine transporters as well as decreases in the density of serotonin transporters in various parts of the brain. Studies have demonstrated that daily use of methamphetamine results in increased cell death in the brain, which would have a negative effect on prefrontal cortex functioning.Changes in the activity of the dopamine system are associated with reduced motor skills and impaired verbal learning. Studies have also revealed that chronic use of methamphetamine causes severe structural and functional changes in those areas of the brain associated with emotion and memory, which could explain many of the emotional and cognitive problems observed in chronic abusers of the substance.

These neurological changes have given rise to deficits in execution memory which are manifested in a reduced ability to problem solve, increased impulsivity and risky decision-making. Further dysfunctions include apathy, poor self-control and poor executive control. Over time, methamphetamine destroys the dopamine receptors in the brain, which has the effect of reducing the ability to feel pleasure.The use of methamphetamine has been proven by a number of studies to be associated with irreversible damage to the brain and, even though the neurotransmitters in the brain may recover over time, damage to cognitive abilities cannot be reversed.