Study findings suggest that disrupted auditory attention is observed in bipolar disorder (BD) patients independent of their mood state, medication status, or history of psychotic features, but may be influenced by the presence of a comorbid anxiety disorder.

Previous studies have shown that BD patients show aberrations of event-related potential (ERP) measures of auditory processing elicited during “oddball” discrimination tasks, in which infrequent target tones presented within a series of frequent distracter tones must be identified.

“Aberrations in auditory ERPs may reflect a neurophysiologic marker, or endophenotype, for BD, but the effect of patients’ mood state, current medication usage, or history of other psychiatric disorders on these measures are not well understood,” explain Daniel Fridberg (Indiana University, Bloomington, USA) and co-authors.

The team therefore administered an auditory “oddball” discrimination task to elicit ERPs in 69 patients with type I BD, of whom 14 were unmedicated, and 52 healthy individuals with no history of psychiatric disorders. Patients were placed into subgroups based on whether they were euthymic or symptomatic, and amplitude and peak latency measures from N100, P200, N200, and P300 ERP components were compared across subgroups.

The P300 ERP component is believed to provide an index of selective attention and general cognitive efficiency, with the peak latency believed to represent stimulus evaluation speed independent of reaction time, and its amplitude representing neural activity underlying attention and memory process involved in updating stimulus representations.

N100, P200, and N200 ERP components precede the P300 in time and reflect earlier stages of information processing, the authors explain.

P300 amplitude to target tones was reduced in both the symptomatic and euthymic BD patient groups compared with controls. BD patients also had a prolongation in P300 latency compared with controls, at 408.3 versus 380.4 ms.

Furthermore, symptomatic and euthymic BD patient groups did not differ on P300 amplitude or latency, and also showed reduced P200 amplitude to frequent tones compared with controls.

Regression analysis showed that history of comorbid anxiety disorder diagnosis was associated with reduced N200 peak latency but increased P300 peak latency. No effects of medication status, history of psychotic features, or mood state on ERP measures in BD patients were observed.

Writing in the journal Bipolar Disorders, the team says that “the present study provides further support for auditory P300 amplitude as a candidate endophenotype for BD,” and “indicates that P300 latency may be sensitive to the presence of a comorbid anxiety disorder in BD patients.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2009

Free abstract

• Schizophrenia And Bipolar Disorder Share Genetic Roots
• Mental Illness Was One Of The Costliest Conditions Between 1996 To 2006

Patient reporting and severity of adverse drug reactions (ADRs) during long-term lithium treatment for bipolar disorder are affected by both serum lithium concentration and mood state, say Dutch researchers.

Compared with randomized controlled studies, the effectiveness of lithium treatment for bipolar disorders is lower in naturalistic follow-up, with nonadherence one of the major contributory factors. Previous studies have indicated that ADRs are a major reason for discontinuing treatment.

To determine the impact of mood state and lithium ADRs, Antoine Egberts, from Utrecht University, and colleagues conducted a 26-year follow-up study of 186 patients aged ?18 years treated at an outpatient lithium clinic between 1973 and 2000.

Information on the presence and severity of nine specific ADRs that frequently occur as a result of lithium treatment and can be identified by patients was gathered by a research nurse at each monthly scheduled visit. Serum lithium level and mood state were also assessed at each visit.

In all, 94.6% of patients had at least two ADR questionnaires completed during follow-up, giving a total of 8056 questionnaires. The median duration of patient follow-up was 5.7 years. At least one ADR was reported by all but two patients.

The serum lithium level at each interview was within the therapeutic range for 62.5% of patients, and mood state was rated as euthymic in 73.4% of cases. Adjusting for mood state, serum lithium level was significantly associated with the number of present ADRs, as well as with the average severity of all present ADRs.

Further adjustment for mood state, age at study inclusion, gender, and duration of lithium use confirmed that serum lithium was significantly associated with the number and severity of reported ADRs. Specifically, patients with a serum lithium level of 0.6 mmol/l, 0.9 mmol/l, and 1.2 mmol/l had an average number of ADRs of 3.3, 3.6, and 3.8, respectively.

When adjusting for serum lithium level, there was a significant association between mood state and the average number and severity of ADRs, with depressed mood, euthymic, and manic patients having an average of 2.0, 3.3, and 4.6 ADRs, respectively.

Interestingly, of the ADRs, tiredness and concentration deficits were most strongly linked to mood state, while polyuria and polydipsia were mostly strongly linked to serum lithium level.

The team writes in the journal Bipolar Disorders: “In conclusion, we found that both mood state and lithium serum level are independently associated with the prevalence and the severity of patient-reported ADRs in patients on lithium treatment.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

Free abstract

• First Time-Door Is Open For Family Discussion Of Bipolar Disorder
• FDA Grants Approval For Use Of RISPERDAL(R) CONSTA(R) As Both A Monotherapy And Adjunctive Therapy In The Maintenance Treatment Of Bipolar I Disorder
• Schizophrenia And Bipolar Disorder Share Genetic Roots
• What Rorschach Tests Really Tell Us