In clinical terms, Pollock had a productive manic phase, and he was overtaken by black dog in the days before anti-depressants.
In clinical terms, Pollock suffered from manic depressive disorder. 
mnli hypothesis: In clinical terms, Pollock suffered from manic depressive disorder.  premise: In clinical terms, Pollock had a productive manic phase, and he was overtaken by black dog in the days before anti-depressants.