This programme included Prof. James Fallon of the University of California, Irvine, but did not feature his most telling finding, which may be the subject of the next programme. 
  So, SPOILER ALERT!  




Prof. Fallon studies dangerous psychopaths, and has looked at the positron emission tomograms of such people, finding typical changes among them, that may be pathognomic.  He has been in the scanner himself, to find that he shares the same features of psychopathy as the known killers he has studied!  More, he has learnt from his parents that he has a family history of psychopathy and murder!

Yet he is a pleasant, respected and distinguished academic.   He suspects that his good childhood upbringing may have prevented his genetic inheritance from making him what some of his ancestors were, psychopathic killers.  Which is the same point made about the MAOI gene, that it isnot expressed unless the adult was abused as a child.

Which raises the "association is not causation" argument.   Violent people have been found to have the cerebral features of Prof.Fallon or the MAOI 'warrior' gene.   The programmes do not say how far the opposite may be true, that the possessors of these 'markers' are violent adults, or have neither, with an abused childhood and a violent present.  How many are, like Prof. Fallon, well-adjusted, achieving members of society with those features, is unknown.

 We really don't know what any of this means, yet.

Nor, as Matthew raises in another thread ( http://doc2doc.bmj.com/forums/open-clinical_psychiatry_should-shyness-defined-mental-illness ) do we know what we are doing in defining mental illness.  The murderer in the programme was defended by pleading his 'warrior' gene.  The new edition of the Diagnostic and Statistical Manual, DSM-5, includes, as well as a definition of shyness as a pathology, the diagnoses of "oppositional defianat disorder" for stroppy children, and "paraphilic coercive disorder" to label a rapist.
I wonder how soon that will be raised in court as an excuse?

John