What the possible symptoms of low serotonin in brain, ?

Depression: We have selective serotonin reuptake inhibitors to help with depression or anxiety. Associated symptoms may manifest as trouble with sleep, interests, guilt, energy, concentration, appetite, libido, pain, and mood issues (depression, anxiety, anger, short fuse, irritibility). We do not measure brain serotonin, but surmise that there may be an imbalance if the symptoms suggest it.