Arthur experiences a continuous state of uncontrollable worry and irritability. Most of the time he feels restless, has difficulty concentrating, experiences unwanted worries, and feels jittery and keyed up, even though he doesn't drink coffee. According to the DSM this disorder is called:

Generalized anxiety disorder.

Explanation:

Generalized anxiety disorder: The term generalized anxiety disorder is also referred to as GAD and is often distinguished as an individual having excessive and persistent worry about various things. An individual facing GAD can anticipate different things in a very serious manner and find himself or herself as overly concerned about family, work, health, money, etc and he or she often find it difficult or impossible to control his or her worry related to the life events.

Symptoms: Restlessness, continuous & excessive worry, difficulty concentrating, etc.

Treatment: Psychotherapy including ERP and CBT.