Chronic use depresses the immune response, interferes with the reproductive system, and contributes to lung damage, including asthma, bronchitis, emphysema, and lung cancer. Chronic use is also associated with a motivational syndrome, a condition characterized by apathy, loss of ambition, poor concentration, passivity, and diminished capacity to set and achieve goals. Crucial research about marijuana's effect on the brain is in progress, and there are a great many unanswered questions in this area. It can be dangerous to mix cannabis with other licit or illicit drugs, as it enhances the effects of depressants, increases the impairment of alcohol, and reacts unpredictably when combined with stimulants. Stimulants, such as cocaine and amphetamines, can cause anxiety, panic attacks, agitation, high blood pressure, irregular heart rate, depression, sleeplessness, malnutrition, and hallucinations.
Stimulants can cause rapid addiction.
An overdose can result in seizure and death. Hallucinogens, such as LSD and PCP, cause significant distortion in perception and thinking which contribute to injury and risky behaviors. Intense and often unpredictable emotional reactions can trigger panic attacks or psychotic reactions. Use can exacerbate existing mental health problems. Some hallucinogens may cause heart or lung failure.