Sex matters: acute functional connectivity changes as markers of remission in late-life depression differ by sex

Sex-specific habenular dysconnectivity in patients with late-life depression

There are significant sex differences in the prevalence, symptom presentation, treatment response and brain abnormalities of patients with late-life depression (LLD). The functional connectivity of the habenula has been associated with depressive symptoms and cognitive impairments in patients with LLD. However, sex differences in habenular functional connectivity patterns among LLD patients remain unclear. One hundred and fourteen patients with LLD and 75 healthy controls (HCs) were included in the present study. Resting-state functional magnetic resonance imaging was used to analyse the static and dynamic functional connectivity (sFC and dFC) of the habenula. There were significant interactions between diagnosis (LLD vs. HCs) and sex for the dFC of the left habenula with the left insula, precentral gyrus, angular gyrus, and middle frontal gyrus and for the right habenula with the right middle temporal gyrus. Pairwise comparisons revealed a trend of HC males > HC females and LLD males < HC males for the connections between the left habenula and the left precentral gyrus, angular gyrus and middle frontal gyrus. Conversely, a trend of HC males < HC females and LLD males > HC males was found for the connections between the right habenula and right middle temporal pole. Furthermore, there was a significant interaction for the sFC of the right habenula with the right fusiform gyrus, with trends of HC males > HC females, LLD males < HC males, and LLD females > HC females. Regression analysis revealed that left habenular-left insular dFC was associated with long-delay memory in females and working memory in males; right habenular-right middle temporal pole dFC was associated with information processing speed in females. Sex moderated the relationships between cognitive function (global cognition, delay-recalled memory and working memory) and dFC between the left habenula and left insula. In conclusions, this study revealed sex-specific alterations in the functional connectivity patterns of the habenula in LLD patients, and these alterations were associated with various cognitive functions in a sex-specific manner. These findings provide a neurobiological basis for understanding sex differences in LLD patients.

Treatment-resistant late-life depression prevalence and clinical/sociodemographic correlates: An electronic health records study

BACKGROUND

Treatment-resistant late-life depression (TRLLD) remains a clinical challenge. Our aim was to identify demographic and clinical factors associated with TRLLD.

METHODS

A large naturalistic retrospective cohort study was conducted using mental health records from south London. Patients were selected at first recorded depression diagnosis after the age of 60. We defined TRLLD when ≥3 antidepressants were prescribed across their mental health record or a natural language processing algorithm indicated depression was described as treatment-resistant. We collected demographic and clinical characteristics around the first depressive episode diagnosis at age ≥ 60 and used multivariate logistic regression models to investigate factors associated with TRLLD.

RESULTS

Of 8171 patients with late-life depression, 1443 (17.7 %) had TRLLD. Amongst those with severe, psychotic or recurrent depression the prevalence of TRLLD was 30.7 %, 31.4 % and 27.0 % respectively. Female sex, recurrent, severe, or psychotic depression and higher self-harm risk were associated with higher odds of TRLLD after adjustment for demographics (Adjusted Odds ratio (aOR): 1.36, 2.05, 2.34, 2.21 and 1.30 respectively). Older age, Black ethnicity, cognitive impairment and difficulties in activities of daily living were associated with a lower likelihood of TRLLD (aOR: 0.97, 0.65, 0.71 and 0.76 respectively). Several physical conditions examined were associated with increased odds for TRLLD, the strongest association was with hypertension (aOR: 2.20).

CONCLUSIONS

This is the first large-scale study examining the socio-demographic data as well as psychiatric and physical comorbidities in TRLLD without known dementia. Prevention and management of multi-morbidity should be considered in primary or secondary prevention of treatment-resistant depression.

Seeing more than the Tip of the Iceberg: Approaches to Subthreshold Effects in Functional Magnetic Resonance Imaging of the Brain

Many functional magnetic resonance imaging (fMRI) studies and presurgical mapping applications rely on mass-univariate inference with subsequent multiple comparison correction. Statistical results are frequently visualized as thresholded statistical maps. This approach has inherent limitations including the risk of drawing overly-selective conclusions based only on selective results passing such thresholds. This article gives an overview of both established and newly emerging scientific approaches to supplement such conventional analyses by incorporating information about subthreshold effects with the aim to improve interpretation of findings or leverage a wider array of information. Topics covered include neuroimaging data visualization, p-value histogram analysis and the related Higher Criticism approach for detecting rare and weak effects. Further examples from multivariate analyses and dedicated Bayesian approaches are provided.

Sex differences in brain excitability revealed by concurrent iTBS/fNIRS

Sex differences have been claimed an imperative factor in the optimization of psychiatric treatments. Intermittent theta-burst stimulation (iTBS), a patterned form of repetitive transcranial magnetic stimulation, is a promising non-invasive treatment option. Here, we investigated whether the real-time neural response to iTBS differs between men and women, and which mechanisms may mediate these differences. To this end, we capitalized on a concurrent iTBS/functional near-infrared spectroscopy setup over the left dorsolateral prefrontal cortex, a common clinical target, to test our assumptions. In a series of experiments, we show (1) a biological sex difference in absolute hemoglobin concentrations in the left dorsolateral prefrontal cortex in healthy participants; (2) that this sex difference is amplified by iTBS but not by cognitive tasks; and (3) that the sex difference amplified by iTBS is modulated by stimulation intensity. These results inform future stimulation treatment optimizations towards precision psychiatry.

Functional connectivity of cognition-related brain networks in adults with fetal alcohol syndrome

BACKGROUND

Fetal alcohol syndrome (FAS) can result in cognitive dysfunction. Cognitive functions affected are subserved by few functional brain networks. Functional connectivity (FC) in these networks can be assessed with resting-state functional MRI (rs-fMRI). Alterations of FC have been reported in children and adolescents prenatally exposed to alcohol. Previous reports varied substantially regarding the exact nature of findings. The purpose of this study was to assess FC of cognition-related networks in young adults with FAS.

METHODS

Cross-sectional rs-fMRI study in participants with FAS (n = 39, age: 20.9 ± 3.4 years) and healthy participants without prenatal alcohol exposure (n = 44, age: 22.2 ± 3.4 years). FC was calculated as correlation between cortical regions in ten cognition-related sub-networks. Subsequent modelling of overall FC was based on linear models comparing FC between FAS and controls. Results were subjected to a hierarchical statistical testing approach, first determining whether there is any alteration of FC in FAS in the full cognitive connectome, subsequently resolving these findings to the level of either FC within each network or between networks based on the Higher Criticism (HC) approach for detecting rare and weak effects in high-dimensional data. Finally, group differences in single connections were assessed using conventional multiple-comparison correction. In an additional exploratory analysis, dynamic FC states were assessed.

RESULTS

Comparing FAS participants with controls, we observed altered FC of cognition-related brain regions globally, within 7 out of 10 networks, and between networks employing the HC statistic. This was most obvious in attention-related network components. Findings also spanned across subcomponents of the fronto-parietal control and default mode networks. None of the single FC alterations within these networks yielded statistical significance in the conventional high-resolution analysis. The exploratory time-resolved FC analysis did not show significant group differences of dynamic FC states.

CONCLUSIONS

FC in cognition-related networks was altered in adults with FAS. Effects were widely distributed across networks, potentially reflecting the diversity of cognitive deficits in FAS. However, no altered single connections could be determined in the most detailed analysis level. Findings were pronounced in networks in line with attentional deficits previously reported.