Understanding the psychiatric discussion thus far

In the aftermath of the Sandy Hook massacre, reports have surfaced that shooter Adam Lanza suffered from some sort of mental disability or disorder, the exact nature of which is thus far a matter of dispute. Neighbors have described Lanza as odd, remote, and reclusive ; schoolmates recall him as a brainiac, with a flat affect; and a longtime family friend reveals that Adam lacked the ability to feel pain. His brother, Ryan Lanza, told ABC news that Adam "is autistic, or has Asperger syndrome and a 'personality disorder.'" Police authorities, meanwhile, have alluded to the shooter's "checkered past," calling him a "troubled youth."

Greater diagnostic clarity on this matter will emerge within the next few weeks as friends and doctors who knew Adam Lanza come forward to aid law enforcement in their investigation. Until it does, it may help to understand some of the diagnoses in question:

Autism: Autism is a disorder characterized by difficulty with social interaction and communication, as well as repetitive and restrictive behaviors and interests. It is currently estimated to affect 1 in 88 children born in America. Diagnosis is usually made between ages 2 and 6. While children with severe autism can have violent outbursts, there is no known link between autism and premeditated violence.

Asperger's: Asperger's is considered a type of autism (though there will be a change in nomenclature in 2013). In this disorder, individuals have difficulty with social interaction and demonstrate repetitive and restrictive behaviors, but have no difficulty with communication. People with Asperger's may lack interest in sharing experiences with others, or developing relationships.

Personality Disorder: This refers to a category of psychiatric diagnoses, each related to a lifelong pattern of maladaptive behaviors. In the words of the DSM-IV, psychiatry's diagnostic manual, "a personality disorder is an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the individual's culture." Some of the personality disorders that may be examined in Adam's case include:

- Antisocial Personality Disorder: The DSM-IV's closest analog to psychopathy. People with ASPD tend to be aggressive, remorseless, and deceitful, and lack empathy. Violence - premeditated and otherwise - is strongly associated with this category.

- Schizoid Personality Disorder: These individuals avoid social intimacy, have little interest in relationships, and have limited emotional range - often manifest as blunted affect. It is not the same as schizophrenia, although there is a familial association between the two. There is also a familial association between schizophrenia and insensitivity to pain.

- Avoidant Personality Disorder: These individuals are socially inhibited, feel inadequate, avoid social interaction, and are hypersensitive to criticism.

The combination of a flat affect, analgesia, social avoidance, autism-like features, and premeditated violence defies obvious categorization. Like so many out there with unknowable illnesses, Lanza may have had a case of the NOS, or "not otherwise specified," psychiatric shorthand for an undiagnosable illness. Undiagnosable, however, is not tantamount to untreatable -- which, ultimately, is why any of this diagnostic speculation even matters. The hope is that Lanza's doctors and treatment records can help shed light on what might have gone wrong, and what we can do to prevent future massacres.