Comedown or crashing is the deterioration in mood that happens as a psychoactive drug, typically a stimulant, is either decreasing or is cleared from the blood and thus the cerebral circulation. The improvement and deterioration of mood (euphoria and dysphoria) are represented in the cognitive as high and low elevations; thus, after the drug has "elevated" the mood (a state known as a high), there follows a period of "coming back down," which often has a distinct character from withdrawal in stimulants. Generally, a comedown ("down", "low", sometimes "crash") can happen to anyone as a transient symptom, but in people who are dependent on the drug (especially those addicted to it), it is an early symptom of withdrawal and thus can be followed by others. Various drug classes, most especially stimulants and to a lesser degree opioids and sedatives, are subject to comedowns. A milder analogous mood cycle can happen even with blood sugar levels (thus sugar highs and sugar lows), which is especially relevant to people with diabetes mellitus and to parents and teachers managing children's behavior, as well as in adults with ADHD. Stimulant comedowns are unique in that they often appear very abruptly after a period of focus or high, and are typically the more intensely dysphoric phase of withdrawal than that following complete elimination from the bloodstream. Besides general dysphoria, this phase can be marked by frustration, anger, anhedonia, social withdrawal, and other symptoms characteristic to a milder mixed episode in bipolar disorder. Alertness and other general stimulant effects are still present.

Cocaine dependence is a psychological desire to use cocaine regularly. Cocaine overdose may result in cardiovascular and brain damage, such as: constricting blood vessels in the brain, causing strokes and constricting arteries in the heart; causing heart attacks.

The use of cocaine creates euphoria and high amounts of energy. If taken in large, unsafe doses, it is possible to cause mood swings, paranoia, insomnia, psychosis, high blood pressure, a fast heart rate, panic attacks, cognitive impairments and drastic changes in personality.

The symptoms of cocaine withdrawal (also known as "comedown or crash") range from moderate to severe: dysphoria, depression, anxiety, psychological and physical weakness, pain, and compulsive cravings.

Cocaine is a powerful stimulant known to make users feel energetic, happy, talkative, etc. In time, negative side effects include increased body temperature, irregular or rapid heart rate, high blood pressure, increased risk of heart attacks, strokes and even sudden death from cardiac arrest. Many habitual abusers develop a transient, manic-like condition similar to amphetamine psychosis and schizophrenia, whose symptoms include aggression, severe paranoia, restlessness, confusion and tactile hallucinations; which can include the feeling of insects under the skin (formication), also known as "coke bugs", during binges. Users of cocaine have also reported having thoughts of suicide, unusual weight loss, trouble maintaining relationships, and an unhealthy, pale appearance.