SAD symptoms are not that different from that of depression; difficulty getting out of bed, overeating, and lack of energy can all be connected to it. There could also be a decrease in activity, trouble keeping focused, and irritability. Extreme cases will also include hopelessness and worthlessness, withdrawal from social interaction, and even thoughts of suicide.
Most SAD sufferers already experience a depressive disorder, but the symptoms become more apparent seasonally. Although it is more common for SAD to appear during the colder months, some experience it during the spring and summer instead - with a slight difference in the symptoms, which are insomnia rather than trouble getting out of bed, and weight loss instead of weight gain.