A 45-year-old office manager presents to his primary care physician accompanied by his wife. Over the past two years, he has steadily increased the amount of money he gambles each week at casinos and online poker sites. He often borrows cash from friends and family, lies about his gambling losses, and uses his daughter’s college fund to cover debts. He has made multiple unsuccessful attempts to cut back and reports feeling restless and irritable when he tries to stop. He frequently gambles to escape feelings of anxiety and guilt over his mounting losses and has jeopardized his marriage and job by missing work and neglecting responsibilities. Which diagnosis best explains his presentation?