When you were 20, your brain was different

In your twenties you make more of your own decisions than ever, often in rooms full of friends and drinks. This guide covers what brain science says about judgment and risk at your age. It also explains why the best time to set your limits is before the night starts.

What brain science says about judgment in your twenties

The part of the brain behind your forehead, the prefrontal cortex, helps you plan, prioritize and make good decisions. It is one of the last areas to mature [1].
One well-known model describes two systems. One drives the pull toward reward, and it peaks in the mid-teens. The other handles self-control and catches up slowly. Researchers describe the two as not balancing out until the early to mid-twenties [2].
There's no switch that flips at 25. That number came from early brain-imaging studies whose data stopped around age 20, so 25 became a best guess [3]. A recent study of more than 4,200 people found one long period of brain development running from about age 9 to 32 [3].
People differ a lot in how their thinking skills develop [2]. Your brain is still changing through your twenties [3], and so is everyone else's.

How friends and alcohol raise the stakes

Friends watching. Teens in driving studies took more risks, like running red lights, when friends were with them [2]. In a brain-scan study, teens showed more activity in reward areas and made riskier choices when peers were watching [2]. When social payoffs feel big, they can seem to outweigh the possible costs [1]. Not all risk is bad, though. Talking to someone new is a risk too [1].
Charged moments. In socially or emotionally rewarding situations, like being with friends, out late at night or worked up, the self-control system may not be strong enough to rein things in [2].
Alcohol. Alcohol disrupts how the brain works, which can change mood and behavior and make it harder to think clearly [5]. Among college students, alcohol misuse is linked to car crashes, sexual assaults, violence, injuries and death [4]. The first six weeks of college are an especially vulnerable time for heavy drinking [4].

Why this explains risk but never excuses harm

None of this takes away your responsibility. Brain science can help explain why some risks feel easier in certain moments. It never excuses hurting someone, and it isn't a defense for what you do after drinking. You're an adult, and you're responsible for your choices. Knowing how your judgment works is a reason to plan ahead. Snowden urges readers to "start making active choices" about supporting their developing brain [3].

What you can do: decide your limits ahead of time

Charged moments are when self-control works least well [2]. So make your decisions when you're calm.

Set a drink limit before you go out. A standard drink is 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of spirits [4]. Binge drinking means about 4 or more drinks for women, or 5 or more for men, in roughly two hours [4].
Plan your ride home before the first drink. Drunk-driving crashes and arrests are among the most common harms of college drinking [4].
Decide your lines with other people now. If you aren't sure someone wants what's happening, or you aren't sure you're thinking clearly, stop. Alcohol makes it harder to think clearly [5], so you can't count on making that call well in the moment.
Tell a friend your plan. Peers have a strong pull at this age [1, 2]. When the people around you know your limits, that pull can help you keep them.
Support your brain while it's still developing. Aerobic exercise, learning new things like a language, and managing ongoing stress can all help [3].
Get support if drinking feels out of hand. Counseling and skills training are among the approaches that work for college drinking [4]. Your campus counseling center is a good place to start.

Where to get help

If you or someone else is in danger, call 911.
988 Suicide & Crisis Lifeline: call or text 988, 24/7.
Crisis Text Line: text HOME to 741741, 24/7.
If something sexual happened that worries you, to you or someone else: RAINN National Sexual Assault Hotline, 800.656.HOPE (4673), or text HOPE to 64673, 24/7.
See the Need help now page for more options.