text: will depression make a person nice one minute and hateful the next to the person they love?   yes. as someone who's dealt with depression personally, i can tell you that depression is not just sadness. depression can also cause irritability and mood swings.   "depression is a treatable illness involving an imbalance of brain chemicals called neurotransmitters. it is not a character flaw or a sign of personal weakness. you can’t make yourself well by trying to "snap out of it." although it can run in families, you can’t catch it from someone else. the direct causes of the illness are unclear, however it is known that body chemistry can bring on a depressive disorder, due to experiencing a traumatic event, hormonal changes, altered health habits, the presence of another illness or substance abuse."  symptoms of depression   prolonged sadness or unexplained crying spells  significant changes in appetite and sleep patterns  irritability, anger, worry, agitation, anxiety  pessimism, indifference  loss of energy, persistent lethargy  feelings of guilt, worthlessness  inability to concentrate, indecisiveness  inability to take pleasure in former interests, social withdrawal  unexplained aches and pains  recurring thoughts of death or suicide