From a young age, it was clear Simon did not socialize much. He lived in Kirkville with his mother, probably not even knowing who his father was.  His early life is only shown through flashbacks and dialogue, such as the intro speech, stating he had felt alone his whole life. His only companions may have been his mother and maybe one or two friends, most likely one being Sophie. Its hinted that his mother was, and is, overprotective of him, as by the texts he recieves throughout the game. In his life, Doctor Purnell, Simons therapist, states that hes lived with mental problems during his entire life. They have been proved as anxiety and depression, possibly inflicting negatively on his social life. He says(in the IRL trailer) that said problems stemmed from his loneliness. It is suspected that he is a fan of heavy metal music, per the back of his hoodie and his bag. 

As the game goes on, you begin finding morphine syringes. These syringes can heal you, but it does take a second or two to inject it. When Simon rolls up his sleeve, there are scars in a row on his wrist. This could indicate the fact that he used to self-harm, possibly with a switchblade he obtained.  It is possible to overdose on these if too many are used in too little time. It is recommended to use one when health is quite low. It also replenishes stamina, though mainly good for health. If you do manage to use too many, your screen/vision will become blurry. You can turn this feature off in the Options menu.

When Simon first started college, he met a girl named Sophie. He became fond of her, and soon began developing feelings for her. When he receives a call from her, telling him to meet her on a roof top on the opposite park, he decides to go there. When he arrives, he originally did not know it was her. He begins questioning her stuff, like how she got on the roof, if she knew anything about the gas mask doctor(later revealed to be Dr Purnell), among many other things. After a short conversation, she suggests that they sit at the edge of the roof. Simon finally gathers the courage to tell Sophie that he likes her, however, he would love her if they got to know eachother better. She takes this information well, but.. she says she "wants to get away from everything" and.. takes her own life by jumping off the roof. This leads to the second boss, Carcass.