Those taking drugs for recreational and/or therapeutic purposes need to be extra careful in the summer heat, as they have “a high risk of harm from high temperatures,” according to Those on stimulants, like cocaine and Ritalin, as well as antidepressants or psychiatric medications, need to be especially vigilant.

“High doses of stimulants can produce extremely high body temperatures,” says Zheng-Xiong Xi of the National Institute on Drug Abuse. Even caffeine and alcohol have been shown to increase body temperature.

A high dose of a stimulant, combined with excessive heat, is more likely to harm brain cells — thus upping the risk for overdose and death. By nature, stimulants raise body temperature and disrupt the body’s ability to control it. The effects are exacerbated when outside temperatures climb.

Drug users can be safe by staying cool: Hydrating with water, limiting outdoor exposure and avoiding laborious activities as much as possible are some ways to do so. It is also important to watch over children or elderly people on medications, as they can be especially vulnerable to the drugs’ effects. If someone seems “disoriented or difficult to rouse,” he or she requires medical attention.