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Schizophrenia, bipolar disorder linked with dendritic spine loss

Both schizophrenia and bipolar disorder may be associated with reduced dendritic spine density, frequency and length in the dorsolateral prefrontal cortex, according to recently published data.

Researchers from McLean Hospital and Harvard Medical School’s psychiatry department examined postmortem human brain tissue from individuals with schizophrenia (n=14) and bipolar disorder (n=9), as well as unaffected controls (n=19). Primary endpoints were the number of spines per dendrite, spine density and dendrite length, which were compared among groups. Researchers took into account clinical and demographic factors that could affect the primary endpoints.

Mean spine density in control participants was 0.31 spines/mcm, and was significantly reduced by 10.5% in individuals with bipolar disorder (0.28 spines/mcm; P=.02). In individuals with schizophrenia, mean density was reduced by 6.5%, but was not seen as significant (0.29 spines/mcm; P=.06).

A mean of 92.8 spines per dendrite was found in control participants. It was reduced by 25.8% in those with bipolar disorder (68.9 spines per dendrite; P=.005), and 21.6% in those with schizophrenia (72.8 spines per dendrite; P=.003).
Mean dendrite length in control participants was 301.8 mcm, and was reduced by 18.6% in those with bipolar disorder (245.6 mcm; P=.005) and 18.3% in those with schizophrenia (246.5 mcm; P=.005).

Researchers reported clinical variables had no significant effect on the number of spines per dendrite in either the schizophrenia or the bipolar disorder group. Among individuals with schizophrenia, abuse or dependence of alcohol and cannabis was associated with increased spine density, while treatment with lithium was associated with longer dendrites.

“The current study suggests that spine pathology is common to both schizophrenia and bipolar disorder,” the researchers wrote. “Moreover, the study of the mechanisms underlying the spine pathology might reveal additional similarities and differences between the two disorders, which could lead to the development of novel biomarkers and therapeutics.”

Disclosure: One researcher served as a consultant for Abbvie Laboratories and En Vivo.