Can EEG asymmetry patterns predict future development of anxiety and depression?: A preliminary study

Previous research has shown that those reporting symptoms of depression and anxiety tend to exhibit greater relative right frontal electroencephalographic (EEG) activity. Thus, Davidson [Davidson, R.J., 1995. Cerebral asymmetry, emotion, and affective style. In: Davidson, R.J., Hugdahl, K. (Eds.), Brain Asymmetry. MIT, Cambridge, pp. 361-387] has suggested that greater relative right anterior activity may act as a vulnerability marker for the development of depression and anxiety disorders. This study therefore examined whether anterior and posterior EEG asymmetry patterns predicted anxiety and depressive symptoms one year later. At time 1, participants completed the Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI) and had baseline EEG activity recorded. Participants then completed the BDI and STAI one year later. Those with relatively greater EEG activity in the right anterior region reported greater trait anxiety one year later. These preliminary results suggest that relative right frontal EEG activity may predict future development of anxiety symptoms.     

Frontal EEG asymmetry moderates the effects of stressful life events on internalizing symptoms in children at familial risk for depression

This study examined whether frontal alpha electroencephalographic (EEG) asymmetry moderates the association between stressful life events and depressive symptoms in children at familial risk for depression. Participants included 135 children ages 6 to 13, whose mothers had either a history of depression or no history of major psychiatric conditions. Frontal EEG was recorded while participants watched emotion-eliciting films. Symptoms and stressful life events were obtained via the Child Behavior Check List and a clinical interview, respectively. High-risk children displayed greater relative right lateral frontal activation (F7/F8) than their low-risk peers during the films. For high-risk children, greater relative left lateral frontal activation moderated the association between stressful life events and internalizing symptoms. Specifically, greater relative left lateral frontal activation mitigated the effects of stress in at-risk children.     

Electroencephalographic frontal asymmetry and depressive symptoms in the elderly

Although neurophysiological changes of aging are well known, there is still much to learn about cortical asymmetry in older depressed subjects. This study aimed at assessing differences between depressed and normal elderly subjects on alpha asymmetry, and to observe the correlations of this measure with depressive symptoms and quality of life. Thirty-six subjects (14 normal and 22 depressed) were assessed by EEG, depression rating scales, and SF-36. Despite the fact that compared to healthy elderly, depressive elderly subjects showed relatively greater right frontal activity (F4F3) and relatively greater left parietal activity (P4P3); this difference was not significant. The relationship between depression and frontal asymmetry was better observed in healthy elderly, where relatively greater left frontal activity was associated with less depressive symptoms.     

The oft‐neglected role of parietal EEG asymmetry and risk for major depressive disorder

Relatively less right parietal activity may reflect reduced arousal and signify risk for major depressive disorder (MDD). Inconsistent findings with parietal electroencephalographic (EEG) asymmetry, however, suggest issues such as anxiety comorbidity and sex differences have yet to be resolved. Resting parietal EEG asymmetry was assessed in 306 individuals (31% male) with (n=143) and without (n=163) a DSM‐IV diagnosis of lifetime MDD and no comorbid anxiety disorders. Past MDD+ women displayed relatively less right parietal activity than current MDD+ and MDD? women, replicating prior work. Recent caffeine intake, an index of arousal, moderated the relationship between depression and EEG asymmetry for women and men. Findings suggest that sex differences and arousal should be examined in studies of depression and regional brain activity.     

The stability of resting frontal electroencephalographic asymmetry in depression

Although resting frontal electroencephalographic (EEG) alpha asymmetry has been shown to be a stable measure over time in nonclinical populations, its reliability and stability in clinically depressed individuals has not been fully investigated. The internal consistency and test-retest stability of resting EEG alpha (8-13 Hz) asymmetry were examined in 30 women diagnosed with major depression at 4-week intervals for 8 or 16 weeks. Asymmetry scores generally displayed good internal consistency and exhibited modest stability over the 8- and 16-week assessment intervals. Changes in asymmetry scores over this interval were not significantly related to changes in clinical state. These findings suggest that resting EEG alpha asymmetry can be reliably assessed in clinically depressed populations. Furthermore, intraclass correlation stability estimates suggest that although some traitlike aspects of alpha asymmetry exist in depressed individuals, there is also evidence of changes in asymmetry across assessment occasions that are not closely linked to changes in depressive severity.     

Polymorphisms of the HTR1a allele are linked to frontal brain electrical asymmetry

Polymorphic variations in genes related to serotonin synthesis, transport, recognition, or degradation may convey subtle changes in serotonin system architecture that may place an individual at risk for psychopathology when faced with life stressors. The relationship between three key serotonin alleles and frontal brain electrical asymmetry, a putative endophenotype of depression, was examined. Risk alleles were hypothesized to predict relatively greater right frontal brain activity regardless of current clinical state. A sample of 313 college-age individuals, spanning a range of depressive severity from no symptomotology to clinically meaningful levels, participated. Resting encephalographic (EEG) activity was recorded from 64 scalp sites on four occasions separated by at least 24 h (two 8-min recording sessions occurring at each occasion). Alpha power asymmetry scores between homologous sites were calculated for each session and then averaged to form a trait metric of asymmetry for each pair. PCR based genotyping was conducted for the HTR1a, HTR2a, and HTTLPR genes. Variations in the HTR1a gene were related to trait EEG asymmetry, regardless of any history of depression. Compared to subjects with at least one non-risk allele, subjects with homozygous HTR1A risk alleles had significantly greater relative right frontal activity at sites F7/F8, F5/F6, and F1/F2. In conclusion, variation in HTR1a can influence trait level brain activity, which may ultimately be indicative of risk for psychopathology.     

A capability model of individual differences in frontal EEG asymmetry

Researchers interested in measuring individual differences in affective style via asymmetries in frontal brain activity have depended almost exclusively upon the resting state for EEG recording. This reflects an implicit conceptualization of affective style as a response predisposition that is manifest in frontal EEG asymmetry, with the goal to describe individuals in terms of their general approach or withdrawal tendencies. Alternatively, the response capability conceptualization seeks to identify individual capabilities for approach versus withdrawal responses during emotionally salient events. The capability approach confers a variety of advantages to the study of affective style and personality, and suggests new possibilities for the approach/withdrawal motivational model of frontal EEG asymmetry and emotion. Logical as well as empirical arguments supportive of this conclusion are presented.     

Is the relationship between frontal EEG alpha asymmetry and depression mediated by implicit or explicit self-esteem?

A robust physiological finding is a higher relative left sided activity in the prefrontal cortex during the experience of positive approach related emotions and a higher relative right sided activity during the experience of negative withdrawal related emotions. Since self-esteem can be conceptualized within a framework of approach/withdrawal tendencies, the present study aimed at investigating if the relation between frontal EEG alpha asymmetry and depressive symptoms is mediated by implicit or explicit self-esteem. Self-esteem was measured by questionnaires (explicit) and in an indirect way (implicit). The mediation analyses showed that only explicit self-esteem acted as a partial mediator in the path from EEG alpha asymmetry to depression.     

Approaching dysphoric mood: State-effects of mindfulness meditation on frontal brain asymmetry

Meditation-based interventions reduce the relapse risk in recurrently depressed patients. Randomized trials utilizing neurophysiologic outcome measures, however, have yielded inconsistent results with regard to a prophylactic effect. Although frontal brain asymmetry, assessed through electroencephalographic (EEG) alpha activity (8–13 Hz), is indicative of approach vs. withdrawal-related response dispositions and represents a vulnerability marker of depression, clinical trials have provided mixed results as to whether meditation has beneficial effects on alpha asymmetry. Inconsistencies might have arisen since such trials relied on resting-state recordings, instead of active paradigms under challenge, as suggested by contemporary notions of alpha asymmetry.     

Worsening of depressive symptoms 6 months after an acute coronary event in older adults is associated with impairment of cardiac autonomic function

Background: Depression increases mortality of coronary patients, and autonomic dysfunction has been proposed as an explanation for this association. Methods: In a sample of 38 adults ≥ 60 years with myocardial infarction or unstable angina, we studied depression (presence of a major depressive episode and 21-item Hamilton depression score) and heart rate variability (HRV) of 550 normal beats shortly after admission to the coronary care unit (CCU). Thirty patients were alive at 6 months and were studied at that time as well. Spectral HRV measurements included power in the high-frequency range (HF, 0.15—0.55 Hz, a measure of parasympathetic activity) and low-frequency range (LF, 0.03—0.15 Hz). Nonspectral HRV measurements included standard deviation of normal beats (SDNN) and two measures of vagal activity: percentage of adjacent cycles differing by >50 ms (pNN50) and the root-mean-square of differences in successive beats (rMSNN). Results: Patients who died within 6 months (n=8) had a higher Hamilton-D score than survivors (13.9±6.5 vs. 18.4±5.6, P=0.039) and were more likely to have an episode of major depression upon admission to the CCU (71 vs. 27%, P=0.027). An increase in Hamilton-D score at 6 months correlated with a decrease in total (r=–0.48, P=0.014), high-frequency (r=–0.49, P=0.007), and low-frequency HRV (r=–0.46, P=0.014). Limitations: Patients belonged to a single institution and there was a small proportion of men. Conclusions: Progression of mood symptoms 6 months after an acute coronary event is associated with an impairment of autonomic control of the heart in elderly individuals.     

Trajectories of resting frontal brain activity and psychopathology in female adolescents exposed to child maltreatment

Resting frontal electroencephalogram (EEG) alpha asymmetry patterns reflecting different affective and motivational tendencies have been proposed as a putative mechanism underlying resilience among maltreated youth. This 2‐year prospective study examined whether developmental stability of resting frontal alpha asymmetry moderated the relation between child maltreatment severity and psychopathology in female adolescents (n = 43; ages 12–16) recruited from child protection agencies. Results identified two trajectories of resting frontal asymmetry: 60.5% displayed stable right and 39.5% displayed stable left frontal alpha asymmetry. Although individuals with these alpha asymmetry profiles experienced comparable childhood trauma severity, adolescents with stable left alpha asymmetry and lower levels of trauma were less likely to present symptoms or an episode of posttraumatic stress disorder (PTSD) and depression over 2 years than those with stable right alpha asymmetry and lower levels of trauma. These findings suggest that developmental patterns of resting left frontal brain activity may buffer against psychopathology in maltreated female youth.     

Effects of Lateralized Presentations of Faces on Self-Reports of Emotion and EEG Asymmetry in Depressed and Non-Depressed Subjects

Recent data suggest that individuals with affective disorders show anomolies on various measures of cerebral lateralization and hemispheric activation. In this study, EEG was recorded from left and right frontal and parietal scalp regions during left and right visual field and foveal presentations of happy, sad and neutral faces in 10 depressed and 10 non-depressed subjects. The sample was selected from a student population on the basis of scores on the Beck Depression Inventory. Faces were presented for 8 seconds and EOG was used to exclude trials associated with eye movements. Alpha activity from each of the leads during the middle 6 seconds of each trial was extracted for analysis. In addition, subjects were asked to rate each face on the degree to which it depicted various emotions, as well as the degree to which they experienced various emotions in response to each presentation. The results indicated that non-depressed subjects report more happiness in response to RVF compared with LVF presentations of the identical faces while depressed subjects show the opposite pattern. Frontal EEG alpha asymmetry paralleled the subjective ratings of happiness for both groups and accounted for more than 50% of the variance in self-reports of this emotion. Parietal asymmetry showed little relationship to subjective reports of emotion but did show systematic differences as a function of stimulus location, primarily due to changes in right parietal alpha. Finally, depressed subjects showed reciprocal relationships between frontal and parietal asymmetry while non-depressed subjects showed a positive relationship between asymmetry in these regions. The implications of these data for cognitive dysfunction in depression are discussed.     

Manipulation of frontal EEG asymmetry through biofeedback alters self-reported emotional responses and facial EMG

Individual differences in resting asymmetrical frontal brain activity have been found to predict subsequent emotional responses. The question of whether frontal brain asymmetry can cause emotional responses has yet to be addressed. Biofeedback training designed to alter the asymmetry of frontal brain activity was therefore examined. Eighteen right-handed female participants were randomly assigned to receive biofeedback training designed to increase right frontal alpha relative to left frontal alpha (n = 9) or to receive training in the opposite direction (n = 9). Five consecutive days of biofeedback training provided signals of reward or nonreward depending on whether the difference between right (F4) and left (F3) frontal alpha exceeded a criterion value in the specified direction. Systematic alterations of frontal EEG asymmetry were observed as a function of biofeedback training. Moreover, subsequent self-reported affect and facial muscle activity in response to emotionally evocative film clips were influenced by the direction of biofeedback training.     

A comparison of the central effects of different progestins used in hormone replacement therapy

Objective: To evaluate the central effect exerted by different progestins used for hormone replacement therapy. Methods: Randomised, placebo-controlled study. One hundred-twenty postmenopausal women on continuous hormonal replacement therapy with transdermal estradiol (50 μg per day) associated, for 10 days every 28 days, with four different progestins: dydrogesterone (DYD; 10 mg per day; n=20), medroxyprogesterone acetete (MPA; 10 mg per day; n=20), nomegestrol acetate (NMG; 5 mg per day; n=20) or norethisterone acetate (NETA; 10 mg per day; n=20). Other 40 women, 10 for each treatment group, were used as controls and were monitored for a single cycle of 28 days during the administration of transdermal estradiol plus placebo. Morning basal body temperature (BBT) was monitored for 28 days. Anxiety, by the state-trait anxiety inventory, and depression, by the self-evaluation depression scale of Zung, were evaluated just prior to and in the last 2 days of the 10-day progestins adjunct. Results: All progestins except DYD increased (P<0.0001) BBT by 0.3–0.5 °C. Anxiety was decreased by DYD (−2.3+1.1; P<0.01) and MPA (−1.5+0.5; P<0.01), but not by NMG or NETA. Depression did not significantly increase during progestins and actually decreased during MPA (−3.0+0.7; P<0.01). Only the effect of DYD on anxiety and that of MPA on depression were significant versus the control group (P<0.05). Conclusions: Different progestins exert different central effects. DYD has the peculiarity of not increasing BBT and of decreasing anxiety, which is also decreased by MPA. Depression is not negatively affected by the tested progestins and it may be ameliorated by MPA. The present data may help to individualise the progestin choice of hormone replacement therapy.     

Right‐frontal cortical asymmetry predicts increased proneness to nostalgia

Nostalgia is often triggered by feelings—such as sadness, loneliness, or meaninglessness—that are typically associated with withdrawal motivation. Here, we examined whether a trait tendency to experience withdrawal motivation is associated with nostalgia proneness. Past work indicates that baseline right‐frontal cortical asymmetry is a neural correlate of withdrawal‐related motivation. We therefore hypothesized that higher baseline levels of right‐frontal asymmetry would predict increased proneness to nostalgia. We assessed participants' baseline levels of frontal cortical activity using EEG. Results supported the hypothesis and demonstrated that the association between relative right‐frontal asymmetry and increased nostalgia remained significant when controlling for the Big Five personality traits. Overall, these findings indicate that individuals with a stronger dispositional tendency to experience withdrawal‐related motivation are more prone to nostalgia.     

Prefrontal brain asymmetry and aggression in imprisoned violent offenders

Anterior brain asymmetry, assessed through the alpha and beta band in resting-state electroencephalogram (EEG) is associated with approach-related behavioral dispositions, particularly with aggression in the general population. To date, the association between frontal asymmetry and aggression has not been examined in highly aggressive groups. We examined the topographic characteristics of alpha and beta activity, the relation of both asymmetry metrics to trait aggression, and whether alpha asymmetry was extreme in anterior regions according to clinical standards in a group of imprisoned violent offenders. As expected, these individuals were characterized by stronger right than left-hemispheric alpha activity, which was putatively extreme in anterior regions in one third of the cases. We also report that in line with observations made in the general population, aggression was associated with stronger right-frontal alpha activity in these violent individuals. This suggests that frontal alpha asymmetry, as a correlate of trait aggression, might be utilizable as an outcome measure in studies which assess the effects of anti-aggressiveness training in violent offenders.     

Influence of psycho-social factors on climacteric symptoms

Background: It has been suggested that psycho-social factors may be crucial in the development of climacteric symptoms. Material and methods: In order to evaluate the effect of psycho-social and biological factors on menopausal symptoms, Greene (climacterical symptoms), Cooper (psychosomatic symptoms of stress), Smilkstein (family dysfunction), Duke-UNC (social support) and Israel (life events) tests were passed to 300 Chilean women between 40 and 59 years of age. Data were evaluated with ANOVA, χ² and logistic regression using the Epi-info package. Results: Perimenopausal women had a significant increase in stress and climacteric symptoms; however comparing with pre and postmenopausal women, tests for life events, family dysfunction or social support did not show any differences. A history of premenstrual syndrome was the main risk predictor f or climacteric symptoms (OR: 3.6, IC: 1.5–8.5; P<0.03), followed by perimenopausal state (OR: 2.9, IC: 1.4–6.0; P<0.001) and negative life events (OR: 2.3, IC: 1.0–5.3; P<0.05). The psycho-social factors were predictors for anxiety and depression; on the other hand, perimenopausal state was a risk factor for somatic and vasomotor symptoms. During premenopause, women with regular cycles and vasomotor symptoms have more psychological symptoms and stress. Conclusion: Climacteric symptoms that appear in the perimenopause are more intense in those women who have a biological predisposition such as premenstrual syndrome and are modulated by psycho-social factors.     

Is extended clonazepam cotherapy of fluoxetine effective for outpatients with major depression?

Background: Clonazepam cotherapy of fluoxetine was previously demonstrated to accelerate efficacy over the first 3 weeks of treatment. A new 18-week double-blind study attempted to replicate these findings to determine whether superiority would extend to 3 months and assess risks of extension. Method: Fifty outpatient volunteers aged 18–65 from Seattle and Portland with moderate-marked depression received fluoxetine (20 mg) doubled at 6 weeks if needed; half took clonazepam (0.5 mg) and half took an identical placebo, 1 or 2 tablets adjusted during the first 2 weeks, until a 3-week taper at 3 months. Results: No serious adverse events and no special problems with sedation or discontinuation were noted. Cotherapy was superior to fluoxetine monotherapy at Day 7 for HAM-D (t=2.03, DF=48, P<0.05) and CGI-I (32 vs. 4% responders, P<0.03, Fisher Exact Test) but not otherwise. Cotherapy was effective in reducing insomnia but not anxiety or core symptoms (low mood, suicidality, reduced interest). The only significant benefit of extending treatment was a more rapid response to increased fluoxetine at 6 weeks manifested in a mean HAM-D of 9.0 and CGI-I responder rate of 76% after 8 weeks compared to 16 weeks for monotherapy. Limitations: Small sample size (N=50) limited power and rendered conclusions tentative. Conclusions: Extended clonazepam cotherapy of fluoxetine appeared safe and effective for depressed outpatients: it was superior to fluoxetine alone early in treatment and again following fluoxetine dose increase. Cotherapy might be considered at the start of fluoxetine treatment, especially for those with insomnia, and when a dose increase of fluoxetine is anticipated.     

Predicting affective responses to exercise using resting EEG frontal asymmetry: Does intensity matter?

Affective responses to exercise may be important for improving adherence to regular programs of exercise. The present study sought to determine whether resting frontal EEG asymmetry, an individual difference measure of affective style, is predictive of affective responses to exercise performed at distinct intensities standardized relative to a metabolic landmark (i.e., the ventilatory threshold, VT). Resting EEG was collected from 30 participants and used to predict affective responses following treadmill running at three exercise intensities: below-VT, at-VT, and above-VT. Affect was assessed [via Activation-Deactivation Adjective Check List, yielding measures of Energetic Arousal (EA) and Tense Arousal (TA)] before, immediately following exercise, after 5 min cool down, and 10 and 20 min post-cool down. Resting mid-frontal asymmetry (F4-F3) significantly predicted EA immediately following below-VT exercise; resting lateral frontal asymmetry (F8-F7) predicted EA at 20 min post-cool down. Resting mid-frontal asymmetry predicted in EA immediately following and following cool down in above-VT exercise. As a whole, frontal asymmetry was predictive of affective responses following exercise, namely greater relative left frontal activity predicting lower EA. This was opposite to the predictions of the valenced motivation model, but may provide some support for the motivation direction model. This is based on the fact that low EA could be indicative of approach motivation, especially at higher exercise intensities.     

Frontal EEG asymmetry and fear reactivity in different contexts at 10 months

Individual differences in observed and maternal-rated fear behaviors and frontal electroencephalogram (EEG) asymmetry were examined in normally developing 10-month-old infants. EEG was recorded during resting baseline, as well as during stranger approach, mask presentation, and toy spider presentation. Mothers completed the Infant Behavior Questionnaire. For mask presentation, baseline and task right frontal EEG asymmetry as well as maternal ratings predicted fear behavior during the mask task. For stranger approach, task-related right frontal EEG asymmetry predicted fear behavior during stranger approach after controlling for baseline asymmetry. There was a trend for task-related right frontal EEG asymmetry to predict fear during presentation of a toy spider after controlling for baseline asymmetry. Maternal report of temperament only added unique variance to the prediction of one fear task after controlling for baseline and task EEG. Assessing fear in multiple situations revealed context-specific individual differences in infant fear.