The mental symptoms associated with Hashimoto's thyroiditis may precede the full-blown, classic picture of hypothyroidism. The psychiatric symptoms include various mental aberrations, depression, irritability, and confusion. Indeed, patients may be mislabeled as having psychotic depression, paranoid schizophrenia, or the manic phase of a manic depressive disorder. The workup must include a thorough evaluation of thyroid function, including tests for autoantibodies. Patients usually respond favorably to thyroid replacement hormone therapy.