Trigger Warning: This post contains language about sexual assault that some readers may find disturbing. This piece is part of Not Your Fault, a Teen Vogue campaign that aims to educate people about the epidemic of sexual assault. For more on this series, click here.

Welcome to "Ask a Sex Educator," a weekly series where renowned sex educator Lena Solow will be answering all of your questions about the tough stuff — sexuality, gender, bodies, STDs, pregnancy, consent, pleasure, and more.

My friend was at a party and got really drunk and had sex with this guy. She said she doesn’t really remember what happened and she’s been acting kind of weird and withdrawn since then. Was she raped?

I’m so sorry your friend had a difficult experience, and I’m so glad you want to support her. From what you're saying, it sounds to me like your friend’s boundaries were crossed. Before I talk about what that means and how to best support her, I want to talk a little bit about alcohol and consent.

When someone is so drunk that they don’t remember what happens the next day, they were too drunk to fully consent — that is, to fully and excitedly say yes to having sex. When someone doesn't consent, that's sexual assault. I hear confusion about this sometimes. People will ask me things like — don't lots of people have drunk sex? How can you know the difference between a little tipsy and too drunk to consent? If both people are wasted, how can one person be assaulting another?

There are a few things people are missing when they ask these questions. First, there are differences between tipsy and incapacitated by alcohol. Of course if you're at all unsure it's best to wait until everyone's sober. But in general, someone who is slurring their words, stumbling, unable to be coherent, or obviously passed out, is too drunk to consent. Additionally, we often mistake issues of alcohol and consent for being about not knowing how drunk someone is. The reality is that people can use alcohol like a date rape drug. That means someone will either push alcohol on someone or seek out an extremely intoxicated person with the intention of taking advantage of that intoxication to cross boundaries. It’s very common for someone to use alcohol as a way to lower someone’s boundaries or ability to consent. Pushing alcohol on someone to the point where they’re incapacitated (slurring words, stumbling, don’t remember what happens the next day) is particularly insidious because it leads to victim blaming people who were drunk when they were assaulted.

Now that you know this, you might reevaluate some things. Do you ever hear people joke about looking for the drunkest girl or person to take home or getting someone really drunk so they can have sex? That's rapey. Shut it down. What do you do if you see a seemingly sober or less drunk person touching or walking off with a really drunk person? From now on, make it a point to check in — ask the drunk person where their friends are and how they're getting home, and tell the sober person that they shouldn't be taking that person home with them. Do you ever leave friends alone when they're really wasted? Time to have a new system. One of the only things that gives me hope when it comes to sexual assault prevention is bystander intervention (intervening when you see something that looks dangerous, even if you don't know the person) and friends looking out for each other, so talk to your friends about how you'll look out for each other.