You’ll be healthier. There’s not a drug out there without some harmful effects as all drugs are basically poisons. The exact effects vary by drug. Heroin or painkillers suppress the action of the lungs and this can lead to tuberculosis, pneumonia or abscesses. Marijuana causes changes to the brain similar to the those that occur with schizophrenia, not to mention the damage to your lungs. Methamphetamine is extremely hard on the entire body, especially the nervous system and brain. The heavy use of many drugs or alcohol leads to extreme weight loss and malnutrition that can affect one’s ability to resist illness.r