Mental illness not same as focal brain lesions

Thomas Insel in his NIMH Director's Blog asks whether a neurological approach to mental illness is helpful. He admits it is an "NIMH mantra" to describe mental disorders as brain disorders. I have previously mentioned his view that mental illnesses are disorders of brain circuits.

He suggests mental illnesses are analogous to heart arrhythmias which may not have a demonstable lesion in the heart. He holds out the hope that mapping patterns of cortical function will find abnormal brain circuitry. The example he gives is of apparent delayed cortical maturation in ADHD. Well, let's see - is this conclusion based on one study ie. Shaw et al (2007), which hasn't been replicated? He also speculates that neuroimaging could allow early detection of so-called circuit disorders.

Insel goes on to state that neuroimaging is beginning to yield biomarkers, but then doesn't say what the biomarkers are. He suggests that deep brain stimulation is demonstrating how changing the activity of specific circuits leads to a remission of refractory depression, but doesn't say what circuits are being changed.

Finally, he at least concedes that, "In truth, we still do not know how to define a circuit". He also concludes that "One thing we can say ... is that earlier notions of mental disorders as chemical imbalances or as social constructs are beginning to look antiquated." Not sure why he includes 'social constructs' in this broadbrush remark, as he's not considered this possibility. His faith in the value of neuroscience to help people recover from mental disorders has been the wish-fulfilling phantasy of modern psychiatry since the 19th century.