Not every change in mood, thinking, or behavior begins with a psychiatric disorder. Thyroid disease can resemble depression, anxiety, or even mania. Anemia and B12, folate, or thiamine deficiencies can cause fatigue and cognitive changes. Sleep apnea can present with poor concentration and low mood. Hormonal and metabolic abnormalities, autoimmune and neurological illnesses, infections, medications, and substance use or withdrawal can all produce symptoms that closely resemble psychiatric illness. A sudden personality change, new symptoms at an unusual age, fluctuating confusion, or symptoms beginning after an illness or medication change deserve particular attention. When the history warrants it, Dr. Rao considers relevant medical conditions, reviews available records, and recommends targeted testing, imaging, or consultation with another physician — because sometimes the most important psychiatric intervention is recognizing the problem isn't primarily psychiatric.