Heroin addiction, like all opiate addiction, occurs when heroin is administered over a sustained period of time. The onset of heroin addiction can be both rapid and severe, dependent on the amount used and frequency in a designated period of time. Heroin addicts will "crave" more of the drug and experience withdrawal symptoms if they do not get their regular "fix" or dose. Not all of the mechanisms by which heroin and other opiates affect the brain are known. Likewise, the exact brain mechanisms that cause tolerance and addiction are not completely understood. Heroin stimulates a "pleasure system" in the brain. This system involves neurons in the mid-brain that use the neurotransmitter called "dopamine." These mid-brain dopamine neurons project to another structure called the nucleus accumbens which then projects to the cerebral cortex. This system is responsible for the pleasurable effects of heroin and for the addictive power of the drug.

Like other drug addictions, heroin can become the most important aspect of an addict's life. Heroin addicts often have habits that cost $100-$200 a day, which can cause addicts to quickly turn to lives of shoplifting, burglary, theft, drug dealing, and prostitution to support their habits. Methadone is a drug that has been used for several decades to treat heroin addiction by blocking heroin’s effects. Methadone generally entails the entire spectrum of opioid side effects, including the development of tolerance and physical and psychological dependence.

A generation ago, the heroin (colloquially known as "smack") available in the U.S. was barely five percent pure and used by a relatively small percentage of young people because it had to be injected with a needle. Now, it appears smack is back with a vengeance and addiction to heroin is being experienced by large groups of new users.

The Office of National Drug Control Policy issued a report (April 1992, No. 5, pp. 1-6) claiming "a massive increase in heroin use and addiction is not likely." One reason for this was, "...the apparent absence of new initiates (i.e., heroin users with little or no prior drug-using experience)." However, based upon recent news reports and other sources (see the A.T. Forum Web site for News Updates), the ONDCP report appears to have been premature, to say the least.

Just this past February, Attorney General Janet Reno admitted heroin is more plentiful, purer, and less expensive than it was just a few years ago. "If we do not counteract the heroin threat now," she said, "we risk repeating the terrible consequences of the 1980s' cocaine and crack epidemic." Authorities estimate that heroin addiction has increased 20 percent and worldwide production has grown sharply, even as the abuse of other illegal substances is declining.

Reports of problems have sprung-up nationwide. In California, heroin sold in the San Joaquin Valley is cheap, potent, and plentiful. Business is booming in area emergency rooms as two or three overdose cases appear each day. In Colorado, Boulder County officials may establish a methadone clinic for the first time in 16 years to deal with increasing heroin addiction. On the East Coast, heroin is reported to be 40 to 70 percent pure and around $10 for a small packet. The number of heroin-related hospital emergencies has more than doubled in New York City and surrounding areas.

Many drug abusers mistakenly believe inhaling heroin, rather than injecting it, reduces the risks of addiction or overdose. In some areas, "shabanging" (picking up cooked heroin with a syringe and squirting it up the nose) has increased in popularity. Street heroin carries prophetic names: "DOA," "Body Bag," "Instant Death," and "Silence of the Lamb." Rather than scaring off young initiates, the implied danger seems to actually increase the drugs allure.