This is an extraordinary case study. In fact, it's so interesting I fear it will join a number of others in founding a pop-psychiatry around radicalism. I say psychiatry because we're attempting to diagnose and in some places completely divine a plate of mental disorders with the expectation that treatment exists. Reviewing the literature I've come to three conclusions:

1. No evidence exists that linking any set of identified radicals by psychiatric disorder. The OP article explicitly states this.
2. Psychology has yet to present a single conclusive, non-normative profile of radicalism. The article's author strongly hints at this, to the point of digging up an almost tautological point raised by the earliest empirical sociologist he could find.

I suspect radicalization, extremism or whatever you want to call it--if it has any meaning at all--is an extremely conditional phenomenon, I do so with my only evidence being the extraordinary diversity of forms in which it takes (not all considered ill in civil society) and the methods its adherents employs (most if not all more frequently and ably used by people we decidedly deem non-radical). And this is just within the cohort we more clearly understand by the name "Islamic terrorist."