Linkage disequilibrium mapping of the chromosome 6q21-22.31 bipolar I disorder susceptibility locus

We previously reported genome-wide significant evidence for linkage between chromosome 6q and bipolar I disorder (BPI) by performing a meta-analysis of original genotype data from 11 genome scan linkage studies. We now present follow-up linkage disequilibrium mapping of the linked region utilizing 3,047 single nucleotide polymorphism (SNP) markers in a case-control sample (N = 530 cases, 534 controls) and family-based sample (N = 256 nuclear families, 1,301 individuals). The strongest single SNP result (rs6938431, P = 6.72 x 10(-5)) was observed in the case-control sample, near the solute carrier family 22, member 16 gene (SLC22A16). In a replication study, we genotyped 151 SNPs in an independent sample (N = 622 cases, 1,181 controls) and observed further evidence of association between variants at SLC22A16 and BPI. Although consistent evidence of association with any single variant was not seen across samples, SNP-wise and gene-based test results in the three samples provided convergent evidence for association with SLC22A16, a carnitine transporter, implicating this gene as a novel candidate for BPI risk. Further studies in larger samples are warranted to clarify which, if any, genes in the 6q region confer risk for bipolar disorder.

Association study of 21 circadian genes with bipolar I disorder, schizoaffective disorder, and schizophrenia

OBJECTIVE

Published studies suggest associations between circadian gene polymorphisms and bipolar I disorder (BPI), as well as schizoaffective disorder (SZA) and schizophrenia (SZ). The results are plausible, based on prior studies of circadian abnormalities. As replications have not been attempted uniformly, we evaluated representative, common polymorphisms in all three disorders.

METHODS

We assayed 276 publicly available 'tag' single nucleotide polymorphisms (SNPs) at 21 circadian genes among 523 patients with BPI, 527 patients with SZ/SZA, and 477 screened adult controls. Detected associations were evaluated in relation to two published genome-wide association studies (GWAS).

RESULTS

Using gene-based tests, suggestive associations were noted between EGR3 and BPI (p = 0.017), and between NPAS2 and SZ/SZA (p = 0.034). Three SNPs were associated with both sets of disorders (NPAS2: rs13025524 and rs11123857; RORB: rs10491929; p < 0.05). None of the associations remained significant following corrections for multiple comparisons. Approximately 15% of the analyzed SNPs overlapped with an independent study that conducted GWAS for BPI; suggestive overlap between the GWAS analyses and ours was noted at ARNTL.

CONCLUSIONS

Several suggestive, novel associations were detected with circadian genes and BPI and SZ/SZA, but the present analyses do not support associations with common polymorphisms that confer risk with odds ratios greater than 1.5. Additional analyses using adequately powered samples are warranted to further evaluate these results.

Effectiveness of adjunctive antidepressant treatment for bipolar depression

BACKGROUND

Episodes of depression are the most frequent cause of disability among patients with bipolar disorder. The effectiveness and safety of standard antidepressant agents for depressive episodes associated with bipolar disorder (bipolar depression) have not been well studied. Our study was designed to determine whether adjunctive antidepressant therapy reduces symptoms of bipolar depression without increasing the risk of mania.

METHODS

In this double-blind, placebo-controlled study, we randomly assigned subjects with bipolar depression to receive up to 26 weeks of treatment with a mood stabilizer plus adjunctive antidepressant therapy or a mood stabilizer plus a matching placebo, under conditions generalizable to routine clinical care. A standardized clinical monitoring form adapted from the mood-disorder modules of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, was used at all follow-up visits. The primary outcome was the percentage of subjects in each treatment group meeting the criterion for a durable recovery (8 consecutive weeks of euthymia). Secondary effectiveness outcomes and rates of treatment-emergent affective switch (a switch to mania or hypomania early in the course of treatment) were also examined.

RESULTS

Forty-two of the 179 subjects (23.5%) receiving a mood stabilizer plus adjunctive antidepressant therapy had a durable recovery, as did 51 of the 187 subjects (27.3%) receiving a mood stabilizer plus a matching placebo (P=0.40). Modest nonsignificant trends favoring the group receiving a mood stabilizer plus placebo were observed across the secondary outcomes. Rates of treatment-emergent affective switch were similar in the two groups.

CONCLUSIONS

The use of adjunctive, standard antidepressant medication, as compared with the use of mood stabilizers, was not associated with increased efficacy or with increased risk of treatment-emergent affective switch. Longer-term outcome studies are needed to fully assess the benefits and risks of antidepressant therapy for bipolar disorder. (ClinicalTrials.gov number, NCT00012558 [ClinicalTrials.gov].).

Validity of the distinction between primary and secondary substance use disorder in patients with bipolar disorder: data from the first 1000 STEP-BD participants

The validity of a primary/secondary substance use disorder (SUD) distinction was evaluated in the first 1000 patients enrolled in the Systematic Treatment Enhancement Program for Bipolar Disorder. Patients with primary SUD (n = 116) were compared with those with secondary SUD (n = 275) on clinical course variables. Patients with secondary SUD had fewer days of euthymia, more episodes of mania and depression, and a greater history of suicide attempts. These findings were fully explained by variations in age of onset of bipolar disorder. The order of onset of SUDs was not linked to bipolar outcomes when age of onset of bipolar disorder was statistically controlled. The primary/secondary distinction for SUD is not valid when variations in the age of onset of the non-SUD are linked to course characteristics.

Prevalence and correlates of tobacco use in bipolar disorder: data from the first 2000 participants in the Systematic Treatment Enhancement Program

OBJECTIVE

Only a few small descriptive studies have examined the prevalence and correlates of tobacco use among bipolar patients. We predicted that poorly controlled manic, depressed and mixed states, and the presence of psychotic symptoms, would be associated with a greater prevalence of smoking among patients with bipolar disorder.

METHOD

We examined the prevalence of smoking in a cross-sectional sample of 1904 patients with bipolar disorder enrolled in the National Institute of Mental Health's Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) database. We also examined the relationship between smoking and other factors including: bipolar subtype, current clinical status, illness severity (e.g., number of prior mood episodes), age of bipolar onset, gender, education, socioeconomic status, and concurrent substance use.

RESULTS

At STEP-BD program entry, 31.2% of patients reported that they were smokers. Patients who were male, less educated, and/or had lower income were more likely to be smokers (P<.01). Additionally, patients with rapid cycling, comorbid psychiatric disorders, and/or substance abuse, and those experiencing a current episode of illness were more likely to be smokers (P<.0001). More lifetime depressive and manic episodes as well as greater severity of depressive and manic symptoms were associated with smoking (P<.001). Use of atypical antipsychotic medications was more prevalent among smokers (P=.04).

CONCLUSIONS

Clinical and demographic variables are associated with smoking in this sample of bipolar patients. Longitudinal analyses are needed to determine how mood and bipolar symptoms interact with smoking over the episodic course of bipolar disorder. Additional studies should focus on whether controlling bipolar symptoms is associated with cessation of smoking.

Serotonin gene polymorphisms and bipolar I disorder: focus on the serotonin transporter

The pathogenesis of bipolar disorder may involve, at least in part, aberrations in serotonergic neurotransmission. Hence, serotonergic genes are attractive targets for association studies of bipolar disorder. We have reviewed the literature in this field. It is difficult to synthesize results as only one polymorphism per gene was typically investigated in relatively small samples. Nevertheless, suggestive associations are available for the 5HT2A receptor and the serotonin transporter genes. With the availability of extensive polymorphism data and high throughput genotyping techniques, comprehensive evaluation of these genes using adequately powered samples is warranted. We also report on our investigations of the serotonin transporter, SLC6A4 (17q11.1-q12). An insertion/deletion polymorphism (5HTTLPR) in the promoter region of this gene has been investigated intensively. However, the results have been inconsistent. We reasoned that other polymorphism/s may contribute to the associations and the inconsistencies may be due to variations in linkage disequilibrium (LD) patterns between samples. Therefore, we conducted LD analyses, as well as association and linkage using 12 polymorphisms, including 5HTTLPR. We evaluated two samples. The first sample consisted of 135 US Caucasian nuclear families having a proband with bipolar I disorder (BDI, DSM IV criteria) and available parents. For case-control analyses, the patients from these families were compared with cord blood samples from local Caucasian live births (n = 182). Our second, independent sample was recruited through the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD, 545 cases, 548 controls). No significant associations were detected at the individual polymorphism or haplotype level using the case-control or family-based analyses. Our analyses do not support association between SLC6A4 and BDI families. Further studies using sub-groups of BDI are worthwhile.

Cerebrospinal fluid corticotropin-releasing factor concentrations in patients with anxiety disorders and normal comparison subjects

Cerebrospinal fluid (CSF) concentrations of corticotropin-releasing factor (CRF) were measured in a group of patients with anxiety disorders and normal comparison subjects (NC) to explore the hypothesis that abnormalities in CRF neuronal regulation occur in patients with anxiety disorders. Analysis of variance (ANOVA) revealed no differences in CSF CRF concentrations between the four diagnostic categories: panic disorder (PD), generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), and NCs. Male OCD patients had higher CSF CRF concentrations than men with PD and GAD and male NCs. CSF CRF concentration was positively correlated with age in women but not in men. These findings suggest that central neuronal CRF regulation may be affected by both age and gender.

Chronicity of symptoms in combat veterans with PTSD treated by the VA mental health system

Self-report questionnaire data, collected at two stages of treatment, are presented for a group of 40 combat veterans with PTSD treated within the VA mental health system. Patients completed the Beck Depression Inventory, Mississippi Scale, and Dissociative Experiences Scale prior to treatment at a PTSD outpatient clinic and at midtreatment follow-up. Patients' symptom reports at follow-up were not correlated with length of time in treatment. Further, results suggest that patients' self-reported symptoms on these measures do not show evidence of improvement after entry into the VA mental health system. Explanations for this apparent chronicity of symptoms are discussed.

Clonazepam-related sexual dysfunction in male veterans with PTSD

Medication-induced sexual dysfunction can significantly interfere with patients' quality of life and lead to poor compliance. This retrospective study examined the records of 100 male veterans with post-traumatic stress disorder (PTSD) selected in alphabetical order from an active treatment file of 230 patients. Forty-two patients had received clonazepam (mean maximum dose: 3.4 +/- 1.6 mg/day) at some point during their treatment. Of these, 18 (42.9%) complained of significant sexual dysfunction (primarily erectile dysfunction). Eighty-four patients received diazepam (mean maximum dose: 52.1 +/- 29.7 mg/day), nine received alprazolam (mean maximum dose: 5.2 +/- 2.8 mg/day) and eight received lorazepam (mean maximum dose: 3.8 +/- 2.4 mg/day). None of these patients complained of sexual dysfunction during treatment with these three other benzodiazepines. Our findings suggest that benzodiazepines, particularly clonazepam in the current study, can be a cause of sexual dysfunction in many male patients. Prospective studies comparing the overall clinical utility of various benzodiazepines are indicated in this and other clinic populations.

CSF cholecystokinin octapeptide in patients with bulimia nervosa and in normal comparison subjects

Cholecystokinin octapeptide (CCK-8) appears to modulate appetitive behavior, and in rodents, anxiety-related behavior. The authors studied CCK-8 in patients with bulimia nervosa. CSF concentrations of CCK-8 were measured in 11 drug-free female patients with DSM-III-R-defined bulimia nervosa and in 16 normal subjects. The bulimic patients had significantly lower levels of CCK-8 than the comparison subjects. CCK-8 concentrations were inversely correlated with scores on the anger-hostility, anxiety, and interpersonal sensitivity subscales of the SCL-90-R. They were not significantly correlated with age, percentage of standardized average body weight, or mean weekly frequency of binge eating or vomiting. The results indicate that central CCK-8 abnormalities may play a role in the pathophysiology of bulimia nervosa.

Prevalence of psychiatric disorders in patients with irritable bowel syndrome

Thirty-five patients with irritable bowel syndrome were referred from the gastroenterology service and underwent structured psychiatric interviews to assess the prevalence of psychiatric illness. Thirty-three (94%) of 35 patients were found to have a lifetime prevalence of any Axis I disorder; the predominant diagnoses were mood and anxiety disorders. Theoretical and practical implications of these findings are discussed.

Cerebrospinal fluid thyrotropin-releasing hormone concentrations in patients with anxiety disorders

In a study of 45 patients with anxiety disorders and 11 control subjects, mean cerebrospinal fluid (CSF) concentrations of thyrotropin-releasing hormone (TRH) were not significantly different between nonpsychiatric control subjects and those with panic disorder, generalized anxiety disorder, or obsessive-compulsive disorder. Male subjects, regardless of diagnosis, had significantly higher mean CSF concentrations of TRH than females.

CSF diazepam-binding inhibitor concentrations in panic disorder

Diazepam-binding inhibitor (DBI) is a neuropeptide that has been detected in the brain and cerebrospinal fluid (CSF). Previous studies have suggested the possible role of DBI as a potential endogenous anxiogenic ligand modulating GABAergic transmission at the benzodiazepine-GABA receptor complex. The measurement of DBI immunoreactivity (DBI-IR) in CSF of panic-disorder patients and normal controls was undertaken to assess whether there were differences in the CSF concentration of this peptide to assess possible relationships with other monoamines and peptides. Lumbar CSF was obtained from 18 panic patients (4 men, 14 women) and 9 controls (5 men, 4 women). As a group, no significant differences were found between panic patients' CSF concentration of DBI-IR (1.12 +/- 0.27 pmol/mL) and normal volunteers (1.23 +/- 0.27 pmol/mL). No gender differences were demonstrated. However, we did find a positive correlation between CSF levels of DBI and CSF corticotropin releasing hormone (CRH) in our panic patients.

CSF cholecystokinin concentrations in patients with panic disorder and in normal comparison subjects

Cholecystokinin concentrations in the CSF of 25 patients with panic disorder and 16 normal comparison subjects were ascertained by radioimmunoassay. The patients with panic disorder had significantly lower CSF concentrations of cholecystokinin, which may reflect increased CNS cholecystokinin receptor sensitivity, reduced numbers of receptors, or a compensatory reduction in cholecystokinin octapeptide secondary to theoretically increased central cholecystokinin tetrapeptide activity.

Dopamine blocking activity of clomipramine in patients with obsessive-compulsive disorder

While many data suggest that Obsessive-Compulsive Disorder (OCD) is an illness accompanied by dysregulation of the serotonergic system, interesting clinical evidence and animal studies also suggest possible dysregulation of the dopaminergic (DA) system. In order to determine whether clomipramine (CMI), an antiobsessional agent, is capable of altering DA function, we performed a neuroleptic radioreceptor assay (NRRA) on plasma samples from OCD patients before and after treatment in a double-blind, placebo controlled trial of CMI. CMI produced mild but significant DA D-2 receptor binding activity in an in vitro assay. The degree of dopamine binding activity did not correlate with clinical response to clomipramine. Because it has been suggested that another drug with antiobsessional efficacy, fluoxetine, may also have dopamine blocking properties, it may be speculated that antidopaminergic activity in combination with serotonergic effects is involved in antiobsessional activity of effective agents for some patients.

Panic and phobic disorders in patients with obsessive compulsive disorder

Obsessive compulsive disorder shares numerous clinical features with other anxiety disorders. To study the relationship between OCD and other anxiety disorders, the authors administered the Structured Clinical Interview for DSM-III to 36 OCD patients. Thirty-nine percent (14) of patients reported a lifetime history of panic attacks, and 14% (5) met DSM-III-R criteria for panic disorder at the time of interview. Fourteen percent (5) met criteria for social phobias, and 19% (7) met criteria for simple phobias. Eighteen patients were treated with clomipramine in doses of at least 100 mg/day for 3 months. Patients with a history of other anxiety disorders responded significantly better to clomipramine.

CSF monoamine levels in normal-weight bulimia: evidence for abnormal noradrenergic activity

Normal-weight bulimic patients have disturbed appetite, mood, and neuroendocrine function and often respond to antidepressants. Since these findings suggest abnormalities in brain monoaminergic pathways, the authors measured CSF monoamine concentrations in 27 normal-weight bulimic patients and 14 volunteers. Bulimic patients had a significantly lower mean CSF norepinephrine concentration. Levels of CSF 5-HIAA, the major serotonin metabolite, and CSF HVA, the major dopamine metabolite, were normal, although more frequent binge-eating in bulimic subjects was associated with a significantly lower CSF HVA level. Whether trait- or state-related, monoaminergic disturbances are part of this disorder's neurobiological syndrome. The lower CSF norepinephrine concentration suggests bulimia is not simply a variant of affective disorders.

Phenelzine treatment of panic disorder: lack of effect on pyridoxal phosphate levels

Earlier reports indicated that phenelzine treatment may result in clinically significant reductions of vitamin B6 in some individuals. Sixteen subjects, ages 21-59 years (seven men, nine women) with panic disorder with or without agoraphobia were treated with an average of phenelzine 53.5 mg/day for an average of 10 weeks in an open treatment study. No significant effects on plasma levels of pyridoxal phosphate, the active form of vitamin B6, were discernible in this group, nor was there any clear relationship between pyridoxal phosphate levels and symptoms in the subgroup of five patients who did develop deficiency-type symptoms. Pyridoxine replacement had unclear effects in symptomatic patients.