One of the differences between Protestantism and the Catholic Faith is that Protestants tend to see things in Black and White. Suicide is a sin, always and everywere, would be what most Protestants believe. But then again many also believe that one sin is as bad as another, and once you are “saved” you can’t do anything to loose salvation.
For Catholics we look at one’s intent, and the capacity one has mentally and spiritually to willingly offend God. Suicide, be it shooting ones self in the head, Boxing in a ring until one is so brain damaged that he cannot function and later dies early as a result of the practice, smokes oneself to death, are all considered sinful. However the gravity of that siin, or the very sinfulness of the action is sometimes mitigated by one’s mental status.
Depression which is a real medical illness, or committing suicide when one is drunk lessens the severity of the sin, because one did not have the mental faculties and does not make the choices one would have if they were not drunk. On autopsy around 10-20% of people have a pituitary tumor in their head, the pressure on the Pituitary gland can cause a number of disorders with ones hormones, and can cause Cushings Disease or high levels of Prolactin to be produced. As 95% of these people were not diagnosed while alive, and one of the side effects of the disorders is an excessive hunger and weight gain, it is really not up to you or me to decide if they are sinning or not.
Yes the Catholic Church holds suicide, gluttony, and any number of behaviors to be sinful, but it also looks at each individual case, and grant the benefit of the doubt in favor of that person, unless they make a formal public statement that they reject what the Church teaches, and are sinning willfully. Otherwise we allow God who knows us and our souls to judge us.