Irritability can result from conditions such as:

>anemia
>Attention Deficit Hyperactivity Disorder ADHD, ADD
>bipolar disorder
>combat stress reaction
>depression
>constipation
>diabetes
>dysmenorrhea
>fatigue
>fever
>headache
>hunger
>hyperthermia
>hypothyroidism
>lead poisoning
>mastoiditis
>meningitis
>pain
>schizophrenia
>sleep apnea
>stress
>rabies
>thyroid disease
>menstrual cycle.
>exposure to caesium
>use abuse of certain legal or illegal substances
>Parkinson's disease
>PMS
>PTSD
>certain personality disorders
>emotional/psychological stress