Substance use disorder is a mental health condition where a person uses drugs or alcohol in a way that’s unhealthy. It can often take over their life because they need that substance to function — though it’s not always easy to tell when that’s the case.

Symptoms of substance use disorder

Officially, there are 10 classes of substances doctors refer to when they talk about substance use disorder, including alcohol, tobacco, cannabis (also known as marijuana), opioids (including oxycodone, hydrocodone, fentanyl, and heroin), sedatives (Valium, benzodiazepines), and stimulants (methamphetamine, cocaine, and MDMA). Signs of a problem involving any of these can include:

• Drinking alcohol or using drugs a lot — this may sound obvious, but it could look like using a large amount of a drug at once, using more of it than is prescribed, or using it every day.

• You develop a high tolerance, meaning you need to take more of that substance to feel its effects — needing more and more drinks to feel drunk, for example.

• Your use interferes with your responsibilities or relationships — maybe you’re frequently missing class because you’re hungover, or you find yourself pulling away from friends who don’t want to get high with you or don’t like hanging out with you when you do.

• Your desire or craving for the substance shapes your behaviors — you don’t just use it when it’s around, you frequently make time to get access to it or make sure you don’t run out.

• You feel like you need to hide your substance use (or how much you use it) from others, even the people you’re closest to.

• You continue to use drugs or alcohol even after it gets you in trouble or embarrasses you over and over again. Maybe you keep getting sick in public from drinking, or a drug puts you so on edge that you keep picking fights with your friends.

• You continue to use the substance even after it puts you in danger, like an overdose or a car accident — or even a situation where you realize something bad could have happened because you were drunk or high.

• You may have tried to quit or cut back on your substance use but when you tried, you found you just ... couldn’t.

Effects on your brain

It’s important to understand that using drugs or alcohol affects the way your brain works. This isn’t to freak you out — only to explain some of the physical symptoms of substance use disorder and why it can be so hard to quit if you use it a lot or over a long period of time.

People drink alcohol or use drugs for all kinds of reasons, a big one being they can make you feel good. “Good” might mean happy, euphoric, less anxious, sleepy, or calm. And in the short term, the good feeling can make you want to use it again.

But the more you use it, the more of it you need to use to achieve the same feeling because you build up tolerance to its effects. And certain drugs that produce intense feelings of pleasure rewire the brain so that activities that used to make you feel good — eating, listening to music, hanging out with friends — no longer feel pleasurable by comparison.

Getting help

Feeling like you’re not in control of your behavior, even when it’s not the most extreme, can be scary. But there are ways to treat substance use disorder, even when it feels impossible.

If you’re concerned about your substance use, or need help setting healthier limits, reach out to your doctor, a counselor, or a mental health professional. It can also help to talk to someone — a parent, family member, or trusted friend — to support you in making the first move and sticking to your goals.