Final answer:
Lithium use can reduce the size of the hippocampus and decrease the amount of gray matter in patients with bipolar disorder.
Step-by-step explanation:
Studies have shown that lithium use can reduce the size of the hippocampus and decrease the amount of gray matter in patients with bipolar disorder. The hippocampus is a part of the brain involved in memory and mood regulation, and gray matter refers to the regions of the brain that contain mostly cell bodies and synapses.