(CNN)Can drug use contribute to a person's earlier-than-expected death, even if they stopped using long ago? Undoubtedly, yes.
Although each drug causes unique physiological and neurological effects, all drugs overlap in one important way, said Dr. Scott Krakower, assistant unit chief for psychiatry at Zucker Hillside Hospital, New Hyde Park in New York. All drugs cause changes in the brain, some in ways that may be long-lasting or even permanent.
Marijuana contains toxic gases and particles that can harm the lungs. Routine smoking is linked to airway inflammation and increased symptoms of chronic bronchitis. Regular users have a greater likelihood of respiratory infections, including pneumonia.
A few studies have shown that marijuana use in the teen years is associated with an increased risk for an aggressive form of testicular cancer. National Institute on Drug Abuse researchers say early onset of this cancer indicates that just a few years of use may be harmful.
Different still are hallucinogens, such as lysergic acid diethylamide (LSD), or acid; mescaline and peyote; psilocybin, or "magic mushrooms"; and phencyclidine (PCP), or angel dust.
Generally, hallucinogens distort a user's perception of reality, direction, distance and time. Some have effects lasting up to 12 hours. Disoriented, users can become unpredictable, erratic and violent, which can lead to serious injury or even death.
With LSD, in particular, repeat users develop a tolerance, so they tend to take higher and higher doses to achieve the same psychedelic effects. Large doses of LSD are more likely to cause convulsions, coma, heart and lung failure, or death.
Counteracting the harm done
If you've used drugs, you might want to take certain countermeasures. The first one is quitting.
"Though you have used them or tried them in the past, the idea is that if you stop, while some things may be permanent -- the idea is hopefully, our bodies can learn to compensate and move forward the best it can," Krakower said. "Therefore, you want to try and stop earlier rather than later."
Dharia agrees: "Quitting is the first step."
After that, she said, former drug users need to make sure they see their primary care physicians on a regular basis and "be honest" about their history, because "any physician will understand the potential long-term effects of those drugs and what to screen for."
Along with routine doctor visits, former drug users need to exercise regularly, never smoke, avoid excessive alcohol, watch their sugar and eat healthy, said Dharia: "That's everything you can do afterward."