Which biological factor may be involved in the development of mental illness?

Sometimes mental health disorders have biological causes. Some of these biological risk factors include chromosomal and chemical abnormalities, genetic predisposition, medical illness, poor response to medication, poor sleep, substance abuse, brain damage, and already having a mental health disorder.

my hamster died and my second hamster i got after that one died as well. i also lost two birds named rainbow and kiwi, (they didn't die, they flew off and escaped). i lost a cat named omi, and a dog named snoopie. the best way i got over it is, paying my respects, and just thinking that they were in a happy place. as well as just remembering but not thinking about it all the time, just do fun activities and try not to think about it too much. hope you feel better. i'm sorry about your loss. : (