Alzheimer's disease (AD) is the most common cause of dementia, but cognitive decline also occurs in other neurological conditions, such as Parkinson's disease, Lewy body dementia, vascular dementia, and frontotemporal dementia.

A selective serotonin reuptake inhibitor (SSRI) is generally used for initial treatment of major depressive disorder (MDD). A serotonin-norepinephrine reuptake inhibitor (SNRI), bupropion (Wellbutrin SR, and others), and mirtazapine (Remeron, and others) are reasonable alternatives. Improvement in symptoms can occur within the first two weeks of treatment with these drugs, but a substantial benefit may not be achieved for 4-8 weeks.

The FDA has approved the oral second-generation antipsychotic drug brexpiprazole (Rexulti – Otsuka/Lundbeck) for once-daily treatment of agitation associated with dementia due to Alzheimer's disease (AD). Brexpiprazole is the first drug to be approved in the US for this indication. It is also approved for treatment of schizophrenia and as an adjunct to antidepressants for treatment of major depressive disorder.

The FDA has approved an extended-release fixed-dose combination of dextromethorphan and bupropion (Auvelity – Axsome) for treatment of major depressive disorder (MDD) in adults.