This is not an exhaustive list but just a few.
Anxiety disorders happen when someone has feelings of anxiety that are very strong or last for a long time.
Bipolar disorder is characterised by the experience of swings between low mood and high, manic mood, usually with more normal phases in between.
Depression is characterised by the persistence of feelings of sadness or misery.
Eating disorders can occur when someone has a relationship with food that they find difficult.
Obsessive compulsive disorder (OCD) is an anxiety disorder where unwanted thoughts, urges and repetitive activities become an obstacle to living life as someone wants to.
Someone might have a personality disorder if their personality traits cause regular, long-term problems in the way they cope with life.
Schizophrenia is a mental illness that occurs when the parts of the brain that are responsible for emotion and sensation stop working properly.