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Studying phenotypic and genetic characteristics of age at onset (AAO) and polarity at onset (PAO) in bipolar disorder can provide new insights into disease pathology and facilitate the development of screening tools.
To examine the genetic architecture of AAO and PAO and their association with bipolar disorder disease characteristics.
Genome-wide association studies (GWASs) and polygenic score (PGS) analyses of AAO (n = 12 977) and PAO (n = 6773) were conducted in patients with bipolar disorder from 34 cohorts and a replication sample (n = 2237). The association of onset with disease characteristics was investigated in two of these cohorts.
Earlier AAO was associated with a higher probability of psychotic symptoms, suicidality, lower educational attainment, not living together and fewer episodes. Depressive onset correlated with suicidality and manic onset correlated with delusions and manic episodes. Systematic differences in AAO between cohorts and continents of origin were observed. This was also reflected in single-nucleotide variant-based heritability estimates, with higher heritabilities for stricter onset definitions. Increased PGS for autism spectrum disorder (β = −0.34 years, s.e. = 0.08), major depression (β = −0.34 years, s.e. = 0.08), schizophrenia (β = −0.39 years, s.e. = 0.08), and educational attainment (β = −0.31 years, s.e. = 0.08) were associated with an earlier AAO. The AAO GWAS identified one significant locus, but this finding did not replicate. Neither GWAS nor PGS analyses yielded significant associations with PAO.
AAO and PAO are associated with indicators of bipolar disorder severity. Individuals with an earlier onset show an increased polygenic liability for a broad spectrum of psychiatric traits. Systematic differences in AAO across cohorts, continents and phenotype definitions introduce significant heterogeneity, affecting analyses.
Little is known about the impact of insulin resistance on bipolar
To examine the relationships between insulin resistance, type 2 diabetes
and clinical course and treatment outcomes in bipolar disorder.
We measured fasting glucose and insulin in 121 adults with bipolar
disorder. We diagnosed type 2 diabetes and determined insulin resistance.
The National Institute of Mental Health Life Chart was used to record the
course of bipolar disorder and the Alda scale to establish response to
prophylactic lithium treatment.
Patients with bipolar disorder and type 2 diabetes or insulin resistance
had three times higher odds of a chronic course of bipolar disorder
compared with euglycaemic patients (50% and 48.7% respectively
v. 27.3%, odds ratio (OR) = 3.07, P
= 0.007), three times higher odds of rapid cycling (38.5% and 39.5%
respectively v. 18.2%, OR = 3.13, P =
0.012) and were more likely to be refractory to lithium treatment (36.8%
and 36.7% respectively v. 3.2%, OR = 8.40,
P<0.0001). All associations remained significant
after controlling for antipsychotic exposure and body mass index in
Comorbid insulin resistance may be an important factor in resistance to
treatment in bipolar disorder.
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