That depends on what you mean by that. As for content warnings, you have descriptions of domestic abuse, sexual violence, self-harm, suicide, all sorts of dark themes that you might expect in a horror game. The reason why I hesitate to call it strictly 18+ is because there's no nudity and no realistic gore shown or really described in detail. But I would say due to the disturbing themes alone, player discretion is definitely advised. If you aren't sure about the content, feel free to download the demo before playing the paid build - there's a full list of content warnings at the start and you can get a feel for the general atmosphere of the game.
That said I started developing this game at age 15 so I'm not gonna police anyone, but definitely be careful if any of these themes might be triggering for you.