Comedown or crashing is the deterioration in mood that happens as a psychoactive drug is cleared from the blood and thus the cerebral circulation. The improvement and deterioration of mood (euphoria and dysphoria) are represented in the cognitive schema 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. Such a comedown (down, low, 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 opioids, are subject to crashing. 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 dealing with children's behavior.
- Cocaine withdrawal
- Sunday Mornin' Comin' Down (Kris Kristofferson song about the phenomenon)