Medial temporal N-acetyl-aspartate in pediatric major depression

Body mass index and variability in hippocampal volume in youth with major depressive disorder

BACKGROUND

The hippocampus has been implicated in major depressive disorder (MDD), in both adults and youth. However, possible sources of variability for the hippocampus have not been well delineated. Here, we explored the relationship between body mass index (BMI) and hippocampal volume in youth with MDD.

METHODS

Twenty-two controls (9 male, 13 female, 12-24 years), 24 youth with MDD and normal BMI (12 male, 12 female, 14-24 years), and 20 youth with MDD and high BMI (14 male, 6 female, 13-22 years) underwent magnetic resonance (MR) imaging and spectroscopy (1H-MRS). Hippocampal volume was determined through manual tracing of high-resolution anatomical T1 scans, and LCModel quantified neurochemical concentrations. Intracranial volume was used as a covariate in analysis to control for effects of brain volume on hippocampus.

RESULTS

In youth with MDD and normal BMI, right hippocampal volume was reduced (p = 0.006, Bonferroni) and a trend for reduced left hippocampal volume was noted when compared to healthy controls (p = 0.054, Bonferroni). Left hippocampal volumes were negatively associated with BMI in youth with MDD and high BMI group (r = -0.593, p = 0.006). No associations were found between the right hippocampus and BMI and there were no group differences for metabolite concentrations.

LIMITATIONS

Larger sample sizes would enable researchers to explore overweight vs obese groups and effect of sex in MDD-BMI groups.

CONCLUSIONS

BMI may account for some of the variability observed in previous studies of hippocampal volume in MDD, and therefore BMI impacts should be considered in future analyses.

Intermittent theta-burst stimulation moderates interaction between increment of N-Acetyl-Aspartate in anterior cingulate and improvement of unipolar depression

BACKGROUND

Intermittent theta-burst stimulation (iTBS), a novel repetitive transcranial magnetic stimulation (rTMS) technique, appears to have antidepressant effects when applied over left dorsolateral prefrontal cortex (DLPFC). However, its underlying neurobiological mechanisms are unclear. Proton magnetic resonance spectroscopy (¹H-MRS) provides in vivo measurements of cerebral metabolites altered in major depressive disorder (MDD) like N-acetyl-aspartate (NAA) and choline-containing compounds (Cho). We used MRS to analyse effects of iTBS on the associations between the shifts in the NAA and Cho levels during therapy and MDD improvement.

METHODS

In-patients with unipolar MDD (N = 57), in addition to treatment as usual, were randomized to receive 20 iTBS or sham stimulations applied over left DLPFC over four weeks. Single-voxel ¹H-MRS of the anterior cingulate cortex (ACC) was performed at baseline and follow-up. Increments of concentrations, as well as MDD improvement, were defined as endpoints. We tested a moderated mediation model of effects using the PROCESS macro (an observed variable ordinary least squares and logistic regression path analysis modeling tool) for SPSS.

RESULTS

Improvement of depressive symptoms was significantly associated with decrease of Cho/NAA ratio, mediated by NAA. iTBS had a significant moderating effect enhancing the relationship between NAA change and depression improvement.

CONCLUSIONS

Our findings suggest a potential neurochemical pathway and mechanisms of antidepressant action of iTBS, which may moderate the improvement of metabolic markers of neuronal viability. iTBS might increase neuroplasticity, thus facilitating normalization of neuronal circuit function.

Experience during adolescence shapes brain development: From synapses and networks to normal and pathological behavior

Adolescence is a period of dramatic neural reorganization creating a period of vulnerability and the possibility for the development of psychopathology. The maturation of various neural circuits during adolescence depends, to a large degree, on one's experiences both physical and psychosocial. This occurs through a process of plasticity which is the structural and functional adaptation of the nervous system in response to environmental demands, physiological changes and experiences. During adolescence, this adaptation proceeds upon a backdrop of structural and functional alterations imparted by genetic and epigenetic factors and experiences both prior to birth and during the postnatal period. Plasticity entails an altering of connections between neurons through long-term potentiation (LTP) (which alters synaptic efficiency), synaptogenesis, axonal sprouting, dendritic remodeling, neurogenesis and recruitment (Skaper et al., 2017). Although most empirical evidence for plasticity derives from studies of the sensory systems, recent studies have suggested that during adolescence, social, emotional, and cognitive experiences alter the structure and function of the networks subserving these domains of behavior. Each of these neural networks exhibits heightened vulnerability to experience-dependent plasticity during the sensitive periods which occur in different circuits and different brain regions at specific periods of development. This report will summarize some examples of adaptation which occur during adolescence and some evidence that the adolescent brain responds differently to stimuli compared to adults and children. This symposium, "Experience during adolescence shapes brain development: from synapses and networks to normal and pathological behavior" occurred during the Developmental Neurotoxicology Society/Teratology Society Annual Meeting in Clearwater Florida, June 2018. The sections will describe the maturation of the brain during adolescence as studied using imaging technologies, illustrate how plasticity shapes the structure of the brain using examples of pathological conditions such as Tourette's' syndrome and attention deficit hyperactivity disorder, and a review of the key molecular systems involved in this plasticity and how some commonly abused substances alter brain development. The role of stimulants used in the treatment of attention deficit hyperactivity disorder (ADHD) in the plasticity of the reward circuit is then described. Lastly, clinical data promoting an understanding of peer-influences on risky behavior in adolescents provides evidence for the complexity of the roles that peers play in decision making, a phenomenon different from that in the adult. Imaging studies have revealed that activation of the social network by the presence of peers at times of decision making is unique in the adolescent. Since normal brain development relies on experiences which alter the functional and structural connections between cells within circuits and networks to ultimately alter behavior, readers can be made aware of the myriad of ways normal developmental processes can be hijacked. The vulnerability of developing adolescent brain places the adolescent at risk for the development of a life time of abnormal behaviors and mental disorders.

Effects of the antidepressant medication duloxetine on brain metabolites in persistent depressive disorder: A randomized, controlled trial

Background

To assess whether patients with Persistent Depressive Disorder (PDD) have abnormal levels of N-acetyl-aspartate (NAA) and whether those levels normalize following treatment with the antidepressant medication duloxetine. Furthermore, we conducted post hoc analyses of other important brain metabolites to understand better the cellular and physiological determinants for changes in NAA levels.

Methods

We acquired proton (1H) magnetic resonance spectroscopic imaging (MRSI) data on a 3 Tesla (3T), GE Magnetic Resonance Imaging (MRI) scanner in 41 patients (39.9±10.4 years, 22 males) with PDD at two time points: before the start and at the end of a 10-week, placebo-controlled, double-blind, randomized controlled trial (RCT) of the antidepressant medication duloxetine. Patients were randomized such that 21 patients received the active medication and 20 patients received placebo during the 10 week period of the trial. In addition, we acquire 1H MRSI data once in 29 healthy controls (37.7±11.2 years, 17 males).

Findings

Patients had significantly higher baseline concentrations of NAA across white matter (WM) pathways and subcortical gray matter, and in direct proportion to the severity of depressive symptoms. NAA concentrations declined in duloxetine-treated patients over the duration of the trial in the direction toward healthy values, whereas concentrations increased in placebo-treated patients, deviating even further away from healthy values. Changes in NAA concentration did not mediate medication effects on reducing symptom severity, however; instead, changes in symptom severity partially mediated the effects of medication on NAA concentration, especially in the caudate and putamen.

Interpretation

These findings, taken together, suggest that PDD is not a direct consequence of elevated NAA concentrations, but that a more fundamental pathophysiological process likely causes PDD and determines the severity of its symptoms. The findings also suggest that although duloxetine normalized NAA concentrations in patients, it did so by modulating the severity of depressive symptoms. Medication presumably reduced depressive symptoms through other, as yet unidentified, brain processes.

Trial registration

ClinicalTrials.gov NCT00360724.

Brain choline in major depression: A review of the literature

The focus of this review is to provide a synthesis of the current literature on the role of brain choline, as measured by proton magnetic resonance spectroscopy (1H-MRS), in major depressive disorder (MDD). The most recent ¹H-MRS literature review took place over 10 years ago and, reflecting the high level of research on this topic, much has been learned since then. Higher brain choline levels have been linked to an increase in depression, and a cholinergic model for MDD development has been postulated. However, current ¹H-MRS studies have been inconclusive regarding the role of choline in depression. Data from eighty-six peer-reviewed studies were analyzed for a random-effects model meta-analysis. Two significant findings are reported. Papers that did not report segmentation had a significant, moderate effect size. Higher choline concentrations in the frontal lobe were found in depressed patients, both in those who responded to treatment and those who did not, after treatment with psychiatric medication, repetitive transcranial magnetic stimulation, or electroconvulsive therapy. Findings from this review may add to existing information regarding the role of brain choline in MDD. This may provide a future target for treatment and drug development. It also may serve as a biomarker for treatment progress.

A pilot study of hippocampal N-acetyl-aspartate in youth with treatment resistant major depression

BACKGROUND

Smaller hippocampal volumes, as assessed by magnetic resonance imaging (MRI), and proton magnetic resonance spectroscopy (¹H-MRS) indexed alterations in brain metabolites have been identified in adults with major depressive disorder (MDD). Our group has found similar effects in MDD youth. However, this has not been studied in youth with treatment resistant MDD (TRD), nor has the interaction between regional N-acetyl-aspartate and volume deficits. N-acetyl-aspartate is an amino acid in the synthesis pathway of glutamate, and serves a marker of neuronal viability/number.

METHODS

Fifteen typically developing youth (16-22 years of age; 7 males, 8 females) and eighteen youth with TRD (14-22 years of age; 8 males, 10 females) underwent ¹H-MRS and MRI on a 3T scanner. A short echo PRESS protocol was used with voxels in the right and left hippocampi (6mL each). Hippocampal volume was evaluated using FreeSurfer.

RESULTS

Compared with the typically developing group, youth with TRD had lower concentrations of N-acetyl-aspartate in the left hippocampus (p=0.004), and a trend for smaller left hippocampal volume (p=0.067). In TRD subjects, hippocampal N-acetyl-aspartate was inversely correlated with left (r=-0.68, p=0.003) but not right hippocampal volume. Right hippocampal glutamate+glutamine was greater in TRD youth compared to typically developing controls (p=0.007).

CONCLUSIONS

These results suggest a neurochemical and structural deficit in the hippocampi of youth with TRD. These findings fit with the role of N-acetyl-aspartate in glutamate neurotransmission and the effect of glutamate on brain morphology.

Proton spectroscopy study of the dorsolateral prefrontal cortex in youth with familial depression

AIM

Structural, functional, and metabolic changes in the dorsolateral prefrontal cortex (DLPFC) are implicated in the pathogenesis of major depressive disorder (MDD). We used proton magnetic resonance spectroscopy ((1) H-MRS) to examine the metabolite choline (glycerophosphocholine plus phosphocholine), which is used as an index of membrane integrity in the left DLPFC, in adolescents and young adults with MDD who were treatment-resistant and had a positive family history compared to healthy controls. Differences in the choline resonance indicate an imbalance between synthesis and degradation activity of neuronal and glia membrane phospholipids.

METHODS

Seventeen adolescents with MDD and 11 healthy controls underwent (1) H-MRS. A short echo point-resolved spectroscopy (echo time = 30 ms, repetition time = 2000 ms) protocol was used with a voxel (4.5cm(3) , 128 averages) placed within the left DLPFC.

RESULTS

There were significantly increased choline (P = 0.04) and creatine concentrations (P = 0.005) in the left DLPFC of the MDD group compared to controls. In MDD participants, choline concentration correlated with scores on the Beck Depression Inventory (r = 0.41, P = 0.03).

CONCLUSION

Increased left DLPFC choline and creatine levels in depressed adolescents may be biomarkers for the disorder. The increased choline levels may indicate abnormalities in neuronal membrane integrity, and the increased creatine could be reflective of altered energy demands and metabolism.

Hippocampal subfield analysis in medication-naïve female patients with major depressive disorder

BACKGROUND

Hippocampal volume loss is known as the best-replicated finding of structural brain imaging studies on major depressive disorder (MDD). Several evidences suggest localized mechanisms of hippocampal neuroplasticity lead the brain imaging studies on the hippocampus and MDD to perform analyses in the subfield level. The aim of this study was to investigate the differences in total and subfield hippocampal volumes, between medication-naïve female MDD patients and healthy controls, through automated segmentation and volumetric methods.

METHODS

Twenty medication-naïve female patients diagnosed with MDD and 21 age-matched healthy controls, underwent T1-weighted structural magnetic resonance scanning. Total volumes of both hippocampi and subfield regions were calculated by the automated procedure for volumetric measures implemented in FreeSurfer and automated segmentation method by Van Leemput et al.

RESULTS

We observed patients to have significantly smaller volumes of the left hippocampus, subiculum, cornu ammonis 2-3, cornu ammonis 4-dentate gyrus, and right subiculum compared to healthy controls. There were no significant predictors for these subfield region volumes among the illness burden-related parameters including duration of illness, number of depressive episodes, severity of depressive symptoms and memory performances.

LIMITATIONS

Our findings relied on the data of only female participants.

CONCLUSIONS

We found significant volume reductions in several hippocampal subfield regions in medication-naïve female MDD patients. Our results are consistent with neurobiological evidences on hippocampal neuroplasticity in MDD, and replicate previous findings that suggest morphologic changes of hippocampal subfields in MDD patients.

Increased ventricular cerebrospinal fluid lactate in depressed adolescents

BACKGROUND

Mitochondrial dysfunction has been increasingly examined as a potential pathogenic event in psychiatric disorders, although its role early in the course of major depressive disorder (MDD) is unclear. Therefore, the purpose of this study was to investigate mitochondrial dysfunction in medication-free adolescents with MDD through in vivo measurements of neurometabolites using high-spatial resolution multislice/multivoxel proton magnetic resonance spectroscopy.

METHODS

Twenty-three adolescents with MDD and 29 healthy controls, ages 12-20, were scanned at 3T and concentrations of ventricular cerebrospinal fluid lactate, as well as N-acetyl-aspartate (NAA), total creatine (tCr), and total choline (tCho) in the bilateral caudate, putamen, and thalamus were reported.

RESULTS

Adolescents with MDD exhibited increased ventricular lactate compared to healthy controls [F(1,41)=6.98, P=0.01]. However, there were no group differences in the other neurometabolites. Dimensional analyses in the depressed group showed no relation between any of the neurometabolites and symptomatology, including anhedonia and fatigue.

CONCLUSIONS

Increased ventricular lactate in depressed adolescents suggests mitochondrial dysfunction may be present early in the course of MDD; however it is still not known whether the presence of mitochondrial dysfunction is a trait vulnerability of individuals predisposed to psychopathology or a state feature of the disorder. Therefore, there is a need for larger multimodal studies to clarify these chemical findings in the context of network function.

Proton magnetic resonance spectroscopy (MRS) in on-line game addiction

Recent brain imaging studies suggested that both the frontal and temporal cortices are important candidate areas for mediating the symptoms of internet addiction. We hypothesized that deficits of prefrontal and temporal cortical function in patients with on-line game addiction (PGA) would be reflected in decreased levels of N-acetyl aspartate (NAA) and cytosolic, choline containing compound (Cho). Seventy three young PGA and 38 age and sex matched healthy control subjects were recruited in the study. Structural MR and (1)H MRS data were acquired using a 3.0 T MRI scanner. Voxels were sequentially placed in right frontal cortex and right medial temporal cortices. In the right frontal cortex, the levels of NAA in PGA were lower than those in healthy controls. In the medial temporal cortex, the levels of Cho in PGA participants were lower than those observed in healthy controls. The Young Internet Addiction Scale (YIAS) scores and perseverative responses in PGA were negatively correlated with the level of NAA in right frontal cortex. The Beck Depressive Inventory (BDI) scores in the PGA cohort were negatively correlated with Cho levels in the right temporal lobe. To the best of our knowledge, this is the first MRS study of individuals with on-line game addiction. Although, the subjects with on-line game addiction in the current study were free from psychiatric co-morbidity, patients with on-line game addiction appear to share characteristics with ADHD and MDD in terms of neurochemical changes in frontal and temporal cortices.

Cortical thickness in youth with major depressive disorder

BACKGROUND

Studies in adults with major depressive disorder (MDD) have implicated dysregulation of frontal-limbic circuits in the symptomology of this disorder. We hypothesized that the middle frontal gyrus (MFG; a core portion of the dorsolateral prefrontal cortex or DLPFC) and the anterior cingulate (caudal), regions implicated in emotive and cognitive control, would display a reduced cortical thickness in youth with MDD as compared to healthy, non-depressed adolescents.

METHODS

Sixteen healthy control adolescents (17.19 ± 1.87 years; 7 males, 9 females) and thirty MDD participants (16.89 ± 2.01 years; 9 males, 21 females) underwent magnetic resonance imaging (MRI). Cortical thickness analysis was carried out using FreeSurfer software.

RESULTS

Counter to our hypothesis, we observed thicker right and left rostral MFG in MDD adolescents as compared to controls (p = 0.004 and p = 0.005, respectively). Furthermore, the left caudal anterior cingulate cortex was thicker in MDD subjects as compared to controls (p = 0.009). In MDD subjects, there was a significant inverse correlation between age and left MFG thickness (r = -0.45, p = 0.001).

CONCLUSIONS

These results have implications for the developmental trajectory of the frontal lobe in adolescent MDD. The MFG is implicated in the frontal-limbic circuits underlying executive functioning and their interaction with affective processing. Alterations in this region are likely involved with the symptoms of MDD. Limitations include a small sample size and cross sectional design.

Hippocampal volume and internalizing behavior problems in adolescence

Adolescence is characterized by dynamic changes in structural brain maturation. At the same time, adolescence is a critical time for the development of affective and anxiety-related disorders. Individual differences in typically developing children and adolescents may prove more valuable for identifying which brain regions correspond with internalizing behavior problems (i.e., anxious/depressive, withdrawal and somatic symptoms) on a continuous scale compared to clinical studies. Participants were 179 (92 males, 87 females) typically developing children and adolescents between ages 8 and 17. Hippocampal and amygdala volumes were measured automatically with FreeSurfer. Internalizing behavior was assessed with the Child Behavior Checklist (CBCL) completed by the parent, and associated with hippocampal and amygdala volumes. Hippocampal volume was inversely related with the total internalizing problems scale of the CBCL, irrespective of gender, age, or informant (mother or father). The effects were most prominent for the withdrawal and anxiety/depression subscales and the left hippocampus: more withdrawal and anxiety/depression was related to smaller left hippocampal volume. No associations were found between internalizing behavior and amygdala volume. This study shows that typically developing children and adolescents with high internalizing behavior share some of the neuroanatomical features of adult depression and anxiety-related disorders.

Hippocampal abnormalities of glutamate/glutamine, N-acetylaspartate and choline in patients with depression are related to past illness burden

BACKGROUND

Smaller hippocampal volumes in major depressive disorder (MDD) have been linked with earlier onset, previous recurrences and treatment refractoriness. The aim of our study was to investigate metabolite abnormalities in the hippocampus associated with past depressive illness burden.

METHODS

Glutamate/glutamine (Glx), N-acetylaspartate (NAA) and choline (Cho), potential markers of glial/neuronal integrity and membrane turnover, respectively, were measured in adults with depression and healthy controls using a 3 T magnetic resonance spectroscopy scanner. Voxels were placed in the head of the right and left hippocampus. We controlled for systematic differences resulting from volume-of-interest (VOI) tissue composition and total hippocampal volume.

RESULTS

Our final sample comprised a total of 16 healthy controls and 52 adult patients with depression in different stages of the illness (20 treatment-resistant/chronic, 18 remitted-recurrent and 14 first-episode), comparable for age and sex distribution. Patients with treatment-resistant/chronic and remitted-recurrent depression had significantly lower levels of Glx and NAA than controls, especially in the right hippocampal region (p ≤ 0.025). Diminished levels of Glx were correlated with longer illness duration (left VOI r = -0.34, p = 0.01). By contrast, Cho levels were significantly higher in patients with treatment-resistant/chronic depression than those with first-episode depression or controls in the right and left hippocampus (up to 19% higher; all p ≤ 0.025) and were consistently related to longer illness duration (right VOI r = 0.30, p = 0.028; left VOI r = 0.38, p = 0.004) and more previous episodes (right VOI r = 0.46, p = 0.001; left VOI r = 0.44, p = 0.001).

LIMITATIONS

The cross-sectional design and the inclusion of treated patients are the main limitations of the study.

CONCLUSION

Our results support that metabolite alterations within the hippocampus are more pronounced in patients with a clinical evolution characterized by recurrences and/or chronicity and add further evidence to the potential deleterious effects of stress and depression on this region.

Toward dysfunctional connectivity: a review of neuroimaging findings in pediatric major depressive disorder

Child and adolescent psychiatric neuroimaging research typically lags behind similar advances in adult disorders. While the pediatric depression imaging literature is less developed, a recent surge in interest has created the need for a synthetic review of this work. Major findings from pediatric volumetric and functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI) and resting state functional connectivity studies converge to implicate a corticolimbic network of key areas that work together to mediate the task of emotion regulation. Imaging the brain of children and adolescents with unipolar depression began with volumetric studies of isolated brain regions that served to identify key prefrontal, cingulate and limbic nodes of depression-related circuitry elucidated from more recent advances in DTI and functional connectivity imaging. Systematic review of these studies preliminarily suggests developmental differences between findings in youth and adults, including prodromal neurobiological features, along with some continuity across development.

MR spectroscopic studies of the brain in psychiatric disorders

The measurement of brain metabolites with magnetic resonance spectroscopy (MRS) provides a unique perspective on the brain bases of neuropsychiatric disorders. As a context for interpreting MRS studies of neuropsychiatric disorders, we review the characteristic MRS signals, the metabolic dynamics,and the neurobiological significance of the major brain metabolites that can be measured using clinical MRS systems. These metabolites include N-acetylaspartate(NAA), creatine, choline-containing compounds, myo-inositol, glutamate and glutamine, lactate, and gamma-amino butyric acid (GABA). For the major adult neuropsychiatric disorders (schizophrenia, bipolar disorder, major depression, and the anxiety disorders), we highlight the most consistent MRS findings, with an emphasis on those with potential clinical or translational significance. Reduced NAA in specific brain regions in schizophrenia, bipolar disorder, post-traumatic stress disorder, and obsessive–compulsive disorder corroborate findings of reduced brain volumes in the same regions. Future MRS studies may help determine the extent to which the neuronal dysfunction suggested by these findings is reversible in these disorders. Elevated glutamate and glutamine (Glx) in patients with bipolar disorder and reduced Glx in patients with unipolar major depression support models of increased and decreased glutamatergic function, respectively, in those conditions. Reduced phosphomonoesters and intracellular pH in bipolar disorder and elevated dynamic lactate responses in panic disorder are consistent with metabolic models of pathogenesis in those disorders. Preliminary findings of an increased glutamine/glutamate ratio and decreased GABA in patients with schizophrenia are consistent with a model of NMDA hypofunction in that disorder. As MRS methods continue to improve, future studies may further advance our understanding of the natural history of psychiatric illnesses, improve our ability to test translational models of pathogenesis, clarify therapeutic mechanisms of action,and allow clinical monitoring of the effects of interventions on brain metabolicmarkers

Distinguishing between major depressive disorder and obsessive-compulsive disorder in children by measuring regional cortical thickness

CONTEXT

Cortical abnormalities have been noted in previous studies of major depressive disorder (MDD).

OBJECTIVE

To hypothesize differences in regional cortical thickness among children with MDD, children with obsessive-compulsive disorder (OCD), and healthy controls.

DESIGN

Cross-sectional study of groups.

SETTING

Children's Hospital of Michigan in Detroit.

PARTICIPANTS

A total of 24 psychotropic drug-naive pediatric patients with MDD (9 boys and 15 girls), 24 psychotropic drug-naive pediatric outpatients with OCD (8 boys and 16 girls), and 30 healthy controls (10 boys and 20 girls).

INTERVENTION

Magnetic resonance imaging.

MAIN OUTCOME MEASURE

Cortical thickness.

RESULTS

In the right hemisphere of the brain, the pericalcarine gyrus was thinner in patients with MDD than in outpatients with OCD (P = .002) or healthy controls (P = .04), the postcentral gyrus was thinner in patients with MDD than in outpatients with OCD (P = .002) or healthy controls (P = .02), and the superior parietal gyrus was thinner in patients with MDD than in outpatients with OCD (P = .008) or healthy controls (P = .03). The outpatients with OCD and the healthy controls did not differ in these regions of the brain. The temporal pole was thicker in patients with MDD than in outpatients with OCD (P < .001) or healthy controls (P = .01), both of which groups did not differ in temporal pole thickness. The cuneus was thinner in patients with MDD than in outpatients with OCD (P = .008), but it did not differ from that in healthy controls. In the left hemisphere, the supramarginal gyrus was thinner in both patients with MDD (P = .04) and outpatients with OCD (P = .01) than in healthy controls, and the temporal pole was thicker in patients with MDD than in both healthy controls and outpatients with OCD (P < .001).

CONCLUSIONS

To our knowledge, this is the first study to explore cortical thickness in pediatric patients with MDD. Although differences in some regions of the brain would be expected given neurobiological models of MDD, our study highlights some unexpected regions (ie, supramarginal and superior parietal gyri) that merit further investigation. These results underscore the need to expand exploration beyond the frontal-limbic circuit.

Review: magnetic resonance spectroscopy studies of pediatric major depressive disorder

Introduction. This paper focuses on the application of Magnetic Resonance Spectroscopy (MRS) to the study of Major Depressive Disorder (MDD) in children and adolescents. Method. A literature search using the National Institutes of Health's PubMed database was conducted to identify indexed peer-reviewed MRS studies in pediatric patients with MDD. Results. The literature search yielded 18 articles reporting original MRS data in pediatric MDD. Neurochemical alterations in Choline, Glutamate, and N-Acetyl Aspartate are associated with pediatric MDD, suggesting pathophysiologic continuity with adult MDD. Conclusions. The MRS literature in pediatric MDD is modest but growing. In studies that are methodologically comparable, the results have been consistent. Because it offers a noninvasive and repeatable measurement of relevant in vivo brain chemistry, MRS has the potential to provide insights into the pathophysiology of MDD as well as the mediators and moderators of treatment response.