Undiagnosed ADHD often plays a quiet but powerful role in shaping mood, motivation, and self-worth. When ADHD goes unrecognized, it can create patterns that slowly wear a person down. Over time, this can lead to the development of mental health issues like depression. This connection affects children, teens, and adults alike. It also shows up differently across generations, especially for those who grew up when ADHD was poorly understood or narrowly defined.