Long term effects Regular use of amphetamines may result in ongoing sleeping problems, anxiety and tension, high blood pressure and a rapid and irregular heartbeat. Other possible long-term effects include: Malnutrition. Amphetamines reduce appetite, resulting in people being less likely to eat properly. Psychosis. Frequent heavy use can cause "amphetamine psychosis". Symptoms may include paranoia as well as delusions, hallucinations and bizarre behaviour. These symptoms usually disappear a few days after the person stops using amphetamines. Reduced resistance to infections. Regular amphetamine users often don’t eat or sleep properly and are generally run down, so their resistance to infections is reduced. Violence. People who use amphetamines regularly or in high quantities may become violent for no apparent reason. Brain damage. There is some evidence that amphetamine use may damage brain cells. This damage can result in reduced memory function and possibly other impairments in thinking.