a-typical vs typical is one of the major distinctions in depression. a-typical involves sleeping lots and eating lots. typical involves not being able to sleep and not wanting to eat. typical has better outcomes with anti-depressants than a-typical - though the majority of people with depression have a-typical.

other distinctions have to do with the severity (intensity) and the time that the depression has been around for.

dysthymia is regarded as 'low grade' depression - not because sufferers say that it is 'low grade' - but because from an objective point of view people with dysthymia are fairly functional. this seems to be something along the lines of a depressive personality / character trait.

depression (rather than dysthymia) is more of an episodic thing rather than a character / personality thing. you can have 'brief adjustment disorder' when your depressive episode is in response to an environmental stressor. that can progress to a depressive episode if it lasts longer... and a major depressive episode if he lasts even longer...

the treatments are fairly much the same. though typical depression responds better than the other varieties to anti-depressants. therapy tends to help all round...