Long-term effects of a heroin addiction include changes to the physiologic and physical structure of the brain that produce an imbalance in hormonal and neuronal systems, explains the National Institute on Drug Abuse. The changes in the brain's white matter alter a heroin addict's ability to make decisions, respond to stressful situations and regulate behavior as the brain deteriorates.
A heroin addiction can result in damage to the heart, lungs and kidneys, according to Narconon. Heroin users exhibit symptoms such as tiny pupils, slow breathing, flushed skin, a runny nose and the tendency to fall asleep quickly. Heroin use can also cause slurred speech, vomiting, constipation, nausea and an inability to eat. Some users begin to scratch their skin, neglect grooming habits and cover their arms with long sleeves to hide evidence of heroin use.
People with a physical dependence to heroin often experience withdrawal symptoms within hours after drug use, explains the National Institute on Drug Abuse. Withdrawal symptoms include restlessness, cold flashes, leg movements, muscle and bone pain, and insomnia. Diarrhea and vomiting are common when heroin users experience withdrawal.
Heroin users experience a pleasurable sensation or rush immediately after using the drug, as the drug converts to morphine once it enters the brain, according to the National Institute on Drug Abuse. Users often experience dry mouth, a heavy feeling in the extremities and a warm flush on the skin.