Final answer:
The false statement about hypomania is that it lasts for at least four days, when in fact, the correct duration is at least four consecutive days for a diagnosis.
Step-by-step explanation:
The false statement about hypomania among the options provided is: Hypomania lasts for at least four days. In actuality, for a diagnosis of hypomania, the elevated, expansive, or irritable mood typically must persist for at least four consecutive days. Both statements A and C are correct; hypomania does involve a distinct period of mood change, and it is not severe enough to cause marked impairment in social or occupational functioning, as stated in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Statement D is also true, as hypomania may progress to mania if symptoms become more severe.