Elsevier

Biological Psychiatry

Volume 63, Issue 12, 15 June 2008, Pages 1171-1177
Biological Psychiatry

Original Article
Electroencephalographic Alpha Measures Predict Therapeutic Response to a Selective Serotonin Reuptake Inhibitor Antidepressant: Pre- and Post-Treatment Findings

https://doi.org/10.1016/j.biopsych.2007.10.009Get rights and content

Background

There is growing evidence that individual differences among depressed patients on electrophysiologic (EEG), neuroimaging, and neurocognitive measures are predictive of therapeutic response to antidepressant drugs. This study replicates prior findings of pretreatment differences between selective serotonin reuptake inhibitor (SSRI) responders and nonresponders in EEG alpha power or asymmetry and examines whether these differences normalize or are stable after treatment.

Methods

Resting EEG (eyes open and closed) was recorded from 28 electrodes (nose reference) in 18 depressed patients when off medication and at the end of 12 weeks of fluoxetine treatment. Clinical response was assessed by an independent rater with the Clinical Global Impression Improvement scale. The EEG data were also obtained for 18 healthy adults matched to patients in gender and age.

Results

Treatment responders had greater alpha power compared with nonresponders and healthy control subjects, with largest differences at occipital sites where alpha was largest. There were also differences in alpha asymmetry between responders and nonresponders at occipital sites. Responders showed greater alpha (less activity) over right than left hemisphere, whereas nonresponders tended to show the opposite asymmetry. Neither alpha power nor asymmetry changed after treatment, and test-retest correlations were high, particularly for alpha power. Alpha power and asymmetry showed reasonable positive predictive value but less negative predictive value.

Conclusions

The findings confirm reports of alpha differences between antidepressant responders and nonresponders and raise hopes for developing EEG tests for selecting effective treatments for patients. The stability of alpha power and asymmetry differences between SSRI responders and nonresponders after treatment suggests that they represent state-independent characteristics.

Section snippets

Subjects

Outpatients between the ages of 20 and 56 attending a university-affiliated depression research clinic were included. Patients were excluded for any of the following reasons: serious suicide risk, seizure disorder, mental disorders secondary to a general medical condition, substance use disorders (including alcohol abuse) within the last 6 months, psychotic disorders, history of significant head trauma, or other neurologic disorder. All patients signed informed consent forms before

Pretreatment Session in Responders, Nonresponders, and Control Subjects

There was a difference in overall alpha power among groups [F(2,33) = 3.19, p = .05], with responders having significantly greater alpha when compared with control subjects (p = .02). The enhanced alpha in responders was most evident at posterior sites where alpha is typically largest (Figure 1). When separately examined at frontal, central, parietal, and occipital regions, the difference in alpha among groups was significant only at occipital sites [F(2,33) = 3.51, p = .04]. Responders had

Discussion

Patients who responded to fluoxetine had greater EEG alpha when compared with healthy control subjects, whereas nonresponders did not differ from control subjects. An excess of alpha has previously been reported for patients having an obsessive-compulsive disorder who responded to an SSRI (14) and in affectively disordered patients who responded to treatment with an antidepressant or secondary treatment with an anticonvulsant or lithium (13, 30). Early studies of resting EEG reported finding

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