Or have early signs of some other noncommunicable illness like diabetes type 2 or hypertension, etc….No one knows. Because, unfortunately long-lasting changes to mood is NOT considered a physical sign. It is considered a psychological sign, caused by emotional and psychological problems. And this might be completely wrong. Even if one has psychological problems, the unlooked for physical motor damage to the body may still be the main reason for the mood change.
Neuromuscular motor damage affecting breathing and regulation of pH could be the underlying cause of some mood disorders and the treatment would be to help fight the upper airway obstruction and to stay away from areas with poor ventilation and unclean air, especially if they spend long periods of time there [eg. school, workplace].
Assuming mood disorders to be due to emotional and psychological difficulties is simplistic, childish and concrete. Any early organ dysfunction will cause dysphoric mood. And respiratory acid base imbalances will cause extremely dysphoric mood, and possibly intoxication [euphoria] and asphyxiation [psychosis, irritability, combativeness]….otherwise known as delirium [all locomotor subtypes].