Schizophrenia with comorbid panic disorder, also known as panic psychosis, appears to be a distinct subtype of schizophrenia, according to a study published in Psychiatry Research.

Patients who have these two psychiatric disorders concomitantly show distinctive cognitive and neuropsychological features, and likely will prove to have a different prognosis and a different biology from that of other patients with schizophrenia, said Dr. Erica Kirsten Rapp of the Mount Sinai School of Medicine, New York, and her associates.

Panic attacks have been reported in 7.1%-47.5% of patients with schizophrenia, depending on the population surveyed and the techniques used to assess them. Similarly, panic disorder has been reported in 4.2%-35%.

In research a decade ago, patients who had comorbid obsessive-compulsive disorder and schizophrenia appeared to have “a distinct set of clinical symptoms, neuropsychological features, and treatment responses, prompting researchers to suggest the existence of a ‘schizo-obsessive disorder.’ ” To assess whether those with comorbid panic disorder and schizophrenia constitute a similar subtype, Dr. Rapp and her colleagues examined 255 inpatients using an extensive battery of cognitive and neuropsychological tests.

In all, 165 of these study subjects were diagnosed as having either schizophrenia or schizoaffective disorder without any accompanying anxiety (the schizophrenia-only group), whereas 39 had comorbid panic disorder (the panic-schizophrenia group) and 51 had a nonpanic anxiety disorder (anxiety-schizophrenia group).

Previous investigators have found higher rates of paranoid schizophrenia among patients with comorbid panic symptoms, so Dr. Rapp and her associates specifically examined the prevalence of paranoia in their study subjects. This prevalence was comparable among the three study groups, with 33.9% of the schizophrenia-only group, 33.3% of the panic-schizophrenia group, and 27.5% of the anxiety-schizophrenia group having paranoia.

Thus, the study findings would not be confounded by a predominance of paranoia in any of the study groups.

The panic-schizophrenia group differed significantly from the schizophrenia-only group in numerous measures. They showed significantly higher IQs, higher verbal IQs, better recall after a delay, more efficient problem-solving and set-switching abilities, better attentional skills, and better verbal fluency. They also performed better than the anxiety-schizophrenia group in problem-solving, attentional skills, and verbal fluency.

“These results suggest that patients with panic and schizophrenia may be more cognitively intact . . . and are less likely to exhibit the level of deficits in executive functioning and overall intelligence that are often considered to be a core feature of schizophrenia,” Dr. Rapp and her colleagues said (Psychiatr. Res. 2012 [doi:10.1016/j.psychres.2012.01.017]).

“It is likely that both the presence of panic symptoms and the better neuropsychological performance are precipitated by [the same] underlying neurobiological factor,” they added.

One possible candidate for this underlying factor is dopamine, which is known to affect executive functioning, positive symptoms in schizophrenia, and panic symptoms.

The panic-schizophrenia group also reported significantly more dysthymia when they were stabilized on medication than did either of the other study groups. This might be related to the fact that they also demonstrated significantly more insight into their illness than did the other patients, a finding that has been reported previously.

Given the superior cognitive performance and relatively intact executive functioning of the panic-schizophrenia group, this superior insight might indicate “a better capacity for metacognition and self-reflection. … It may be that once their acute psychoses had resolved, they were more dysphoric about their experiences and prognosis,” the researchers said. Still, their research contributes to the theory that patients with panic psychosis might “constitute a distinct group within those with schizophrenia.”

This study was supported by the National Institute of Mental Health. No financial conflicts of interest were reported.