A 28-year-old male presents for psychiatric evaluation reporting difficulty concentrating, impulsive spending, racing thoughts, irritability, and decreased need for sleep. He was diagnosed with ADHD at age 8 and took methylphenidate through high school. His current symptoms have worsened markedly over the past 3 months. He describes this period as distinctly different from his baseline, noting he usually sleeps 8 hours but now feels fully rested on 3-4 hours. His speech is pressured, he has started four new business ventures in the past month, and his wife reports his behavior is 'completely different from his normal self.' The most likely current diagnosis is: