Can You Really Become Addicted to a Drug After Just One Hit?

You know the story. The one that says some drugs are so enjoyable, so insidious, that just one try will get you hooked. And you'd be forgiven for believing this as the media really backs the theory. "The Danger In Just One Hit of Cocaine," reports the Daily Mail. "Official: 1-Hit Addiction to Meth No Myth," announces the Times Daily. "It Only Took One Hit to Get Hooked," writes news.com.

But is it actually true? Can a person become addicted to a drug after using it a single time? Before we begin to answer this question, it's important to understand how addictive, such as meth and heroin, work on the brain.

Though their mechanisms differ, most addictive drugs act to release the neurotransmitter that makes us feel good: dopamine. For example, opiates like heroin bind to opiate receptors and block the release of neurotransmitters that counterbalance dopamine release. With the checks and balances turned off, the brain gets flooded with dopamine. By contrast, amphetamines (which are similar in structure to dopamine) enter brain neurons by diffusing directly through neural membranes. Once inside, amphetamines both release dopamine and prevent it from being withdrawn.

When a person takes drugs repeatedly, their reward circuits become desensitized. Because there is more than enough dopamine around, the body stops making its own and simultaneously down-regulates the number of dopamine receptors. This means the person needs drugs just to bring their levels of dopamine back to normal. Without drugs they start feeling flat and lifeless. The person may even begin to experience symptoms such as nausea, chills, cramps, and sweating. It is the presence of these withdrawal symptoms that indicates a physical dependence.

Now, back to the question. Dr. John Edwards and Dr. Peter Connor are addiction medicine specialists working at both the Cambridge Clinic and Abbotsford Hospital in Western Australia, and I've had the privilege of spending time with them as part of my medical degree. They both agree that first of all, addiction isn't really a great word because it brings with it a lot of stigma. Putting this aside however, to be diagnosed as addicted you need physical symptoms of tolerance (you require more of the substance to achieve the desired effect) and withdrawal, alongside impaired control, social impairment, and risky behavior. No drug will achieve this combination after just one hit.

Drugs can't change brain chemistry fast enough to make someone instantly dependent. Indeed, a British study of 72 heroin users in 2002 found that it took on average more than a year for people to become hooked to heroin, and none claimed to have been instantly addicted.

However, some research suggests that while a single hit might not make you and addict straight away, it may "prime" the brain for addiction. According to a study published in Nature in 2001, taking one dose of cocaine may "throw open a window of vulnerability" during which the brain is acutely responsive to further doses. However, as the lead researcher Dr. Antonello Bonci described to the Australian Broadcasting Corporation, "This is not saying that if you try cocaine once you'll be hooked. Millions of people have tried it once and never gone back."

Related: Watch our documentary, 'The Hard Lives of Britain's Synthetic Marijuana Addicts'

Also, check out our documentary on the rehab industry: Dying for Treatment

It is important to state at this point that being physically dependent on a drug doesn't necessarily make one an addict. People suffering from chronic pain who take high levels of opiates will experience tolerance and withdrawal, but are only considered addicts if their behavior towards the drugs starts to change. This includes behaviors such as stealing extra prescriptions or spending their time trying to obtain money for drugs.

Another buzzword that often comes up when people talk about drug addiction is "psychological dependence." This is when a drug becomes central to a person's thoughts, behavior, and emotions. Even though a person might understand the drug is harmful, they feel a strong pull to use it because of the way it makes them feel or the promise of escape it might provide.

I've always believed that it was plausible that a person could become psychologically dependent after one hit. But Connor and Edwards are of a different opinion, and I have come around to their way for thinking. "You're still not dependent at that point. You might change your mind the next day," Connor explains. "It's this element of choice and control that exists early on that means a person is not dependent: once you are dependent, you lose that ability."

John likens the situation to buying ice-cream. "You walk past a Ben and Jerry's stand, have some ice cream and really enjoy it. Then the next day you walk past and think I could really go some more ice cream. Even though you want and enjoy the ice cream, you aren't emotionally dependent on it."

So according to the experts, you can't become addicted to drugs after one hit.

Why then do one hit addiction stories and headlines exist? From my conversation with Connor and Edwards, as well as my own medical experience, it likely comes down to two things. Headlines like these play to fears (especially for parents) and therefore make good copy. And then there's a general lack of understanding about how these drugs work, which leaves a void for people to believe the headlines.

Whatever the motivation, I'm going to leave the final words to Connor. He explained that while you can't get addicted from one dose, "you can't get addicted without at least one dose."

Follow Matilda on Twitter.