I am a college student in the US. This post is regarding my friend Adam (not his real name).

TL;DR at the bottom.

Background: I've been close friends with Adam since high school. We enrolled in the same college, along with many other people in our high school friend group. We have always been close and even joined the same fraternity.

Adam always had a really bright and jovial personality. You really couldn't tell if he was ever sad or angry about anything, as he was always joking around and seemed to be in a perpetually good mood. He seemed to get along with everyone he met and made a lot of friends in his dorm his freshman year. I knew that he struggled with some classes his freshman year, but he wasn't doing that poorly compared to his peers.

In his sophomore (2nd) year, he moved into a house off-campus with some of his friends and he started smoking marijuana pretty frequently. I believe that this may have affected his study habits. I also know that he started taking Adderall/Vyvanse in order to cram for exams, which typically led to sleepless nights and rapid weight loss. His grades started slipping during his sophomore year, but on the outside he was still jovial and seemed happy.

At the end of sophomore year (March/April 2017) he stopped showing up to weekly fraternity meetings and wasn't returning any text messages from me or his other friends. I was understanding at the time, because many college students fall off the radar around the final exam period. However, he still never returned anyone's texts even when summer break started. My friend actually saw Adam at a local park very late at night sitting by himself in the beginning of summer break. Adam lost a significant amount of weight and told my friend that "he's going through some stuff."

After months of not hearing from him, my friends and I formed a group chat to discuss what may be going on in his life. Late in the summer, I decided to show up at his house to see if I could talk to him in person since he was not returning our texts and calls. I knocked on the door, called his phone, and texted him, but he didn't come to the door. As I was leaving, I noticed that there was vomit on his driveway next to his car, and his garage door was open.

My heart dropped after seeing that, so I messaged his older brother who doesn't live in the area anymore. His older brother was surprised to hear all of this and told me that Adam was home alone as his parents were traveling at the time. He told me to check the mailbox - it was packed with uncollected mail.

Adam's older brother got in touch with his parents and they seemed to be aware of the situation. More recently, Adam's brother said that Adam was beginning to seek help. It's been almost 10 months since any of us have talked to him or seen him. He also did not return to college for two semesters since the end of his sophomore year.

I suspect that he was dejected by his grades which led to him isolating himself. And, judging by the vomit on his driveway, I suspect there could be substance abuse involved as well.

We're all worried about him and what he is going through. We want to help but we don't know how. Part of me wants to show up at his house again to talk to him in person, but I now realize that it may be selfish and ignorant to do so. I occasionally send him texts to say that I hope he's doing well and I'm always there to help if he needs me. I know that he won't respond but I hope that he reads them.

In your experience and opinion, what do you think he is going through? What is the best way to communicate that we are here to help and support him, without overwhelming him? Thank you all for your help.

TL;DR: My friend who typically seems very happy and bubbly suddenly stops communicating with his friends and isolated himself, possibly due to bad grades at school. What do you think he is going through, and how can his friends help?