A 28-year-old male presents with depressed mood, insomnia, and difficulty concentrating for 6 weeks. He was laid off from his job 2 months ago and says, "I just can't stop thinking about losing my job." He denies suicidal ideation, anhedonia, guilt, or worthlessness. He is eating and sleeping less but attributes it to stress. He has missed several days of job searching and has been withdrawing from friends. What is the MOST likely diagnosis?