I started to wonder about Kelly and drug use last season and this season someone pointed out that the cat pee smell in Kelly's room on the yacht was the smell you get in a meth users room, so I did a little research. Here are the symptoms of chronic Meth use:
"If it's taken in large doses, methamphetamine's frequent effects are irritability, aggressive behavior, anxiety, excitement, auditory hallucinations, and paranoia along with delusions and psychosis. Meth abusers tend to be violent. Mood changes are also common, and the abuser can rapidly change from friendly to hostile. The paranoia produced by methamphetamine abuse results in suspiciousness, hyperactive behavior, and dramatic mood swings.
Other symptoms are dry skin, premature aging, false sense of confidence and power, low apetite, poor coping skills"
I also read that it causes blood sugar drops that lead to sugar cravings.