Dysthymic depression or dysthymia is continuous daily depression which lasts several years, it may not be as intense as major depression but it is still a serious illness, perhaps even more destructive to a person's life than major depression. Imagine a bout of major depression was an initial 2 week intensive phase then followed by a six-month recovery period, in terms of time off work and debility you could liken this to a bad dose of the flu. It could be argued that one episode like this every 10 years would disrupt a person's life less than spending 8-10 of those 10 years suffering from daily this dysthymic depression. To be classified as dysthymia it must last at least 2 years.
Dysthymia and major depressions can combine where a person has bouts of clinical depression and never really fully returns to normal between bouts of major depressions. This is called double depression.
I recommend people with such severe and continuous depression seriously consider the possibility that they in fact have bipolar syndrome or bipolar syndrome type II which can go undiagnosed for years especially if the manic symptoms are not extreme. Discuss in fine detail the symptoms of bipolar syndrome with a mental health professional to see if you have hidden unrecognised bipolar syndrome. See about bipolar syndrome.
Depression can be characterised by a state of heightened emotional sensitivity with extremely intense painful feelings, think of the archetype of the tortured Russian poet, I believe a lack of serotonin is involved in this type of depression. Alternatively depression can be a low energy condition, the person loses their motivation, interest and enthusiasm; distinctly different to the antsy painful serotonin deficient depression above, I believe a lack dopamine is involved at the root of this type of low energy depression.
With the painful serotonin deficient depression thoughts of suicide would be to end the pain, with dopamine deficient depression interest in suicide would be because life loses meaning and pleasure so what's the point to life carrying going on.
Seasonal Affective Disorder