Bonus points:
After completing the game, watch all of the credits. You will be rewarded with 200 bonus points.

Cheat mode:
Enter J8OL14FD as a case-sensitive name to unlock all levels and sequences.

Alternate endings:
Deplete Lucas' sanity bar in the restaurant when the game starts. He will then be committed into an insane asylum.

In the "Lost Love" level, keep drinking the alcohol under the counter in the kitchen, without taking the medication. After the meter is depleted, Lucas will commit suicide by jumping off the balcony.

In the "Confession" level, get your meter as low as possible. While talking with Marcus, select the "Sick" and "Break Off" options and Lucas will turn himself in to the police.

Deplete Carla's sanity meter and she will resign from the NYPD.

Deplete Tyler's sanity meter. Tyler and Sam leave New York and go to Florida.

Lucas being questioned:
If you are stuck at the point where Lucas is being questioned and do not have enough mental health, intentionally do it wrong a few times and you should succeed.