The phrase ‘chemical imbalance’ has been used loosely for decades. The more accurate modern understanding is that neurotransmitters like serotonin, dopamine, GABA, and norepinephrine don’t simply run too high or too low — they operate within complex networks, and when those networks fall out of rhythm, symptoms like depression, anxiety, mood swings, and sleep problems show up. Brain activity and brain chemistry are tightly linked. When one changes, the other tends to follow.