Posttraumatic cognition change trajectories in veterans with PTSD who completed an intensive Cognitive Processing Therapy treatment program.

Negative posttraumatic cognitions (NPCs) have been linked to symptoms of PTSD and are an important target of cognitive behavioral treatments for PTSD, including Cognitive Processing Therapy (CPT). Yet to be explored are the different change trajectories of NPCs during CPT. Knowledge of such change trajectories could elucidate common NPC change processes within CPT and their relationship to PTSD symptom severity. We examined NPC change trajectories in a group of 443 veterans who completed a 2-week intensive CPT program. We identified four NPC trajectory groups termed start high end high, start high end moderate, start moderate end low, and start low end low. Most of the groups showed an increase in NPCs at the midpoint of treatment before ultimately decreasing. As predicted, baseline PTSD symptom severity predicted change trajectory group membership. Also, NPC change trajectories were associated with PTSD severity at the end of treatment such that individuals in smaller NPC change groups had higher PTSD symptoms at the end of treatment, and vice versa. Clinicians can use this knowledge to make predictions of a particular client's NPC change trajectory and set expectations for what progress in treatment may look like, including normalizing increases in NPCs from the start of treatment.

Using machine learning to predict sudden gains in intensive treatment for PTSD.

Sudden gains have been found in PTSD treatment across samples and treatment modality. Sudden gains have consistently predicted better treatment response, illustrating clear clinical implications, though attempts to identify predictors of sudden gains have produced inconsistent findings. To date, sudden gains have not been examined in intensive PTSD treatment programs (ITPs). This study explored the occurrence of sudden gains in a 3-week and 2-week ITP (n = 465 and n = 235), evaluated the effect of sudden gains on post-treatment and follow-up PTSD severity while controlling for overall change, and used three machine learning algorithms to assess our ability to predict sudden gains. We found 31% and 19% of our respective samples experienced a sudden gain during the ITP. In both ITPs, sudden gain status predicted greater PTSD symptom improvement at post-treatment (t2 W=-8.57, t3 W=-14.86, p < .001) and at 3-month follow-up (t2 W=-3.82, t3 W=-5.32, p < .001). However, the effect for follow-up was no longer significant after controlling for total symptom reduction across the ITP (t2 W=-1.59, t3 W=-0.32, p > .05). Our ability to predict sudden gains was poor (AUC <.7) across all three machine learning algorithms. These findings demonstrate that sudden gains can be detected in intensive treatment for PTSD, though their implications for treatment outcomes may be limited. Moreover, despite the use of three machine-learning methods across two fairly large clinical samples, we were still unable to identify variables that accurately predict whether an individual will experience a sudden gain during treatment. Implications for clinical application of these findings and for future studies are discussed.

Appraisal shifts during reappraisal.

How to model the processes involved in regulating emotions via reappraisal? In two studies, we tested whether reappraisal impacts emotions through shifts along appraisal dimensions. In a first experimental study, 437 students imagined reliving a recent distressing event and rated their appraisals and emotions before and after using reappraisal to feel less negative about the event. Between 19% and 49% of changes to different emotions were statistically mediated by shifts along 10 appraisal dimensions. Latent profile analyses suggested that the appraisal shifts reflected four distinct reappraisal tactics. These findings were conceptually replicated in an intensive longitudinal Study 2, where 168 participants rated their appraisals and emotions in relation to a maximum of three emotional events for 7 days, first within an hour of the event and again in the evening when they also reported on emotion regulation use (1142 observations). Between 22% and 46% of changes to different emotions accompanying reappraisal use were statistically mediated by shifts along appraisal dimensions. Appraisal shifts were less significant for unregulated and otherwise regulated emotion changes. Relative to Study 1, the latent profile analyses of Study 2 revealed two similar and four novel reappraisal tactics reflecting a broader range of events and feelings. Across both studies, all appraisal dimensions were involved in at least one tactic and no dimension in all of them, highlighting the suitability of multivariate profiles over univariate dimensions for modelling reappraisal. These findings suggest that appraisal shift profiles can be part of a useful model of cognitive processes underlying reappraisal. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Characteristics associated with non-suicidal self-injury among veterans seeking military sexual trauma-related mental healthcare.

Military sexual trauma (MST) is a serious issue among Veterans; it is associated with increased rates of posttraumatic stress disorder (PTSD) and nonsuicidal self-injury (NSSI), both of which are correlated with poorer mental health outcomes, including increased suicide risk. Additional insight into the characteristics associated with NSSI among Veterans with MST can help identify individuals at increased risk for suicide and other negative outcomes and improve care for Veterans with a history of MST. The current study was comprised of 327 Veterans referred for MST-related mental health services at a VHA hospital. Participants completed a semi-structured interview for clinical symptoms, including NSSI behaviors. Results of a retrospective chart review revealed a high endorsement of lifetime NSSI (26.9%) with cutting behaviors identified as the most frequently endorsed method. Logistic regression showed personality features, history of cumulative sexual trauma, and younger age were uniquely related to lifetime NSSI. These results corroborate previous findings that show elevated rates of NSSI among Veterans with exposure to trauma. This study expands upon previous findings by examining risk factors specific to treatment-seeking Veterans with a history of MST, which can aid clinical care and risk management procedures in Veteran healthcare.

The Effect of Cognitive-Affective Factors on PTSD and Alcohol Use Symptoms: An Investigation on Rumination, Suppression, and Reappraisal.

Background: Posttraumatic stress disorder (PTSD) and alcohol use disorder (AUD) are mental health conditions that often co-occur. The complexity of this comorbidity is well-documented, though the role of malleable cognitive-affective factors in PTSD/AUD warrants further study. Specifically, attaining a more comprehensive understanding of the role of malleable cognitive-affective factors in individuals with symptoms of PTSD/AUD may have important implications for future research, such as in treatment-seeking individuals. Extant examinations of cognitive-affective factors have demonstrated unique associations of cognitive reappraisal, expressive suppression, and rumination in PTSD symptom severity, though these effects had yet to be explored in subgroups of comorbid PTSD/AUD.Methods: In a sample of trauma-exposed individuals (n = 334) recruited to participate through an internet labor market, we first empirically examined latent subgroups of PTSD/AUD symptoms using latent profile analysis, then included expressive suppression, cognitive reappraisal, and four dimensions in the model to elucidate their role in specific profile patterns of PTSD/AUD symptom typologies.Results: Our results support a four-class model of PTSD/AUD symptoms, with unique predictive effects of expressive suppression, problem-focused thoughts, repetitive thoughts, and anticipatory thoughts on latent profile status.Conclusions: These findings may have important implications for future research focused on examining cognitive-affective patterns as they apply to intervention techniques in treatment-seeking individuals with symptoms of PTSD/AUD.

Who will respond to intensive PTSD treatment? A machine learning approach to predicting response prior to starting treatment.

Despite the established effectiveness of evidence-based PTSD treatments, not everyone responds the same. Specifically, some individuals respond early while others respond minimally throughout treatment. Our ability to predict these trajectories at baseline has been limited. Predicting which individuals will respond to a certain type of treatment can significantly reduce short- and long-term costs and increase the ability to preemptively match individuals with treatments to which they are most likely to respond. In the present study, we examined whether veterans' responses to a 3-week Cognitive Processing Therapy-based intensive PTSD treatment program could be accurately predicted prior to the first session. Using a sample of 432 veterans, and a wide range of demographic and clinical data collected during intake, we assessed six machine learning and statistical methods and their ability to predict fast and minimal responders prior to treatment initiation. For fast response classification, gradient boosted models (GBM) had the highest AUC-PR (0.466). For minimal response classification, elastic net (EN) had the highest mean CV AUC-PR (0.628). Using the best performing classifiers, we were able to predict both fast and minimal responders prior to starting treatment with relatively high AUC-ROC of 0.765 (GBM) and 0.826 (EN), respectively. These results may inform treatment modifications, although the accuracy may not be sufficient for clinicians to base inclusion/exclusion decisions entirely on the classifiers. Future research should evaluate whether these classifiers can be expanded to predict to which treatment type(s) an individual is most likely to respond based on various clinical, circumstantial, and biological features.

Comparing Veterans with Posttraumatic Stress Disorder Related to Military Sexual Trauma or Other Trauma Types: Baseline Characteristics and Residential Cognitive Processing Therapy Outcomes.

The Veterans Health Administration (VHA) has called for improved assessment and intervention for survivors of military sexual trauma (MST) to mitigate deleterious sequalae, including posttraumatic stress disorder (PTSD). Research on the impact of MST-related PTSD (MST-IT) on men is limited, and few studies have examined the differential effects of treatment across genders and MST-IT. Additionally, studies have utilized varying definitions of MST (e.g., sexual assault only vs. including sexual harassment), contributing to disparate outcomes across studies. Utilizing data from 343 veterans seeking residential cognitive processing therapy (CPT) for PTSD in VHA, this study examined the impact of MST-IT and gender on differences in demographic characteristics; pre-treatment severity of PTSD (overall and clusters), depression, and negative posttraumatic cognitions (NPCs); and post-treatment severity of these variables after accounting for pre-treatment severity. Results from 2x2 factorial ANOVAs found no differences in pre-treatment depression or overall PTSD by MST-IT, gender, or their interaction; however, MST-IT survivors presented with greater pre-treatment avoidance, global NPCs, and self-blame. Results from hierarchical linear regression models found only pre-treatment symptom severity significantly predicted post-treatment severity for overall PTSD and all NPCs. These findings suggest veteran survivors of MST-IT appear to benefit similarly from CPT delivered in a VHA residential PTSD program compared to veterans with other index traumas, regardless of gender. Although there were minimal post-treatment differences in PTSD and NPCs by MST-IT status and gender, residual symptoms related to negative cognitions and mood appear to differ across gender and MST-IT status. Specifically, in individuals without MST-IT, post-treatment PTSD symptoms of negative alterations in cognition and mood were higher in men than women. Moreover, women with MST-IT reported more symptoms of depression than both men with MST-IT and women without MST-IT. These findings suggest depressive symptoms decrease through residential PTSD treatment differentially by MST-IT status and gender and warrant further examination.

Fear of pain as a predictor of concurrent and downstream PTSD symptoms.

BACKGROUND: Pain anxiety has been associated with more severe posttraumatic stress disorder (PTSD) symptoms. However, the unique role of individual domains of pain anxiety has yet to be explored in the prediction of PTSD severity. This study examined whether specific pain anxiety domains (i.e., cognitive anxiety, escape/avoidance, fear of pain, and physiological anxiety) predict both concurrent and downstream PTSD symptoms above and beyond other PTSD risk factors. METHOD: Participants were 63 survivors of traumatic events with moderate to high baseline pain treated in the emergency department and assessed for PTSD symptoms and pain anxiety at 3- and 12-months. RESULTS: Three-month pain anxiety domains of fear of pain and physiological anxiety (inversely related) significantly predicted concurrent 3-month PTSD symptoms above and beyond other established PTSD risk factors (i.e., sex, age, pain, and trauma type). However, only 3-month fear of pain significantly predicted 12-month PTSD symptoms. CONCLUSIONS: Findings highlight the relevance of specific pain anxiety domains in concurrent and future PTSD symptoms and suggest the importance of evaluating pain anxiety among patients with PTSD. Interventions focused on increasing willingness to experience and tolerate fear of pain may help mitigate this risk, thereby improving outcomes for individuals with acute PTSD symptoms.

Dispositional optimism mediates relations between childhood maltreatment and PTSD symptom severity among trauma-exposed adults.

BACKGROUND: Experiences of maltreatment in childhood, such as abuse and neglect, have been associated with poorer psychological well-being in adulthood, including elevated risk of revictimization and increased likelihood of developing posttraumatic stress disorder (PTSD) symptoms. Maltreatment has also been associated with reduced resources related to resilience, such as optimism, which may act as a protective factor for mental health. OBJECTIVES: In this study, we examined the mediating role of dispositional optimism in the relationship between childhood maltreatment and PTSD symptom severity from recent trauma in a sample of adults (n = 108) who presented to their local emergency department following trauma. METHODS: We analyzed six models to account for cumulative childhood maltreatment as well as five primary subtypes of maltreatment: emotional abuse, physical abuse, sexual abuse, emotional neglect, and physical neglect. RESULTS: Greater dispositional optimism mediated relations between total maltreatment and decreased PTSD severity (Bab = .056, SE = .029, 95 % CI [.009, .121]). Optimism also mediated relations between all maltreatment subtypes and PTSD severity, except sexual abuse. CONCLUSIONS: These results may suggest optimism and positive psychology interventions as effective techniques in reducing the likelihood of PTSD development and severity in trauma-exposed individuals.

A machine learning approach to modeling PTSD and difficulties in emotion regulation.

Despite evidence for the association between emotion regulation difficulties and posttraumatic stress disorder (PTSD), less is known about the specific emotion regulation abilities that are most relevant to PTSD severity. This study examined both item-level and subscale-level models of difficulties in emotion regulation in relation to PTSD severity using supervised machine learning in a sample of U.S. adults (N=570). Participants were recruited via Amazon's Mechanical Turk (MTurk) and completed self-report measures of emotion regulation difficulties and PTSD severity. We used five different machine learning algorithms separately to train each statistical model. Using ridge and elastic net regression results in the testing sample, emotion regulation predictor variables accounted for approximately 28% and 27% of the variance in PTSD severity in the item- and subscale-level models, respectively. In the item-level model, four predictor variables had notable relative importance values for PTSD severity. These items captured secondary emotional responding, experiencing emotions as out-of-control, difficulties modulating emotional arousal, and low emotional granularity. In the subscale-level model, lack of access to effective emotion regulation strategies, lack of emotional clarity, and emotional nonacceptance subscales had the highest relative importance to PTSD severity. Results from analyses modeling a probable diagnosis of PTSD based on DERS items and subscales are presented in supplemental findings. Findings have implications for developing more efficient, targeted emotion regulation interventions for PTSD.

The mediating effect of rumination between posttraumatic stress disorder symptoms and anger reactions.

OBJECTIVE: The relationship between posttraumatic stress disorder (PTSD) and anger is well established. However, further investigation into the underlying mechanisms of this PTSD-anger relationship is needed. Rumination, a construct with a known association to PTSD symptoms, theoretically may mediate this PTSD-anger relationship. DESIGN: We conducted a mediational model using self-report measures of PTSD symptoms, rumination, and anger reactions from a nonclinical, trauma-exposed sample (N = 339) through Amazon's Mechanical Turk. RESULTS: Rumination mediated overall PTSD symptoms and anger reactions, controlling for age and gender identity. Further analyses examined this mediating role between PTSD subscale scores and anger. Rumination mediated all PTSD subscales and anger when modeled separately. After adjusting for other PTSD symptoms, only 2 subscales' relationship with anger remained mediated by rumination: negative alterations in cognitions/mood and physiological arousal. CONCLUSIONS: Rumination should be assessed in the context of PTSD and anger symptoms, specifically physiological arousal and negative moods/cognitions symptoms in PTSD. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Emotional avoidance and social support interact to predict depression symptom severity one year after traumatic exposure.

Individuals exposed to a traumatic event commonly develop symptoms of depression, a psychiatric disorder associated with a number of negative clinical and public health consequences. Both intrapersonal and interpersonal risk factors have been associated with heightened risk for depression following traumatic event exposure; however, less is known about how these risk factors may interact to predict trauma-exposed individuals' risk of subsequently developing depression symptoms. This study examined the interactive influence of emotional avoidance (an intrapersonal risk factor) and perceived social support (an interpersonal risk factor) on the development of depression symptoms over a one-year period among N = 46 individuals recruited shortly after visiting a hospital emergency department for treatment following exposure to a traumatic event. Results revealed a significant main effect of emotional avoidance on 12-month depression symptoms. The main effect was qualified by an emotional avoidance by perceived social support interaction: the relation of emotional avoidance to 12-month depression symptoms was positive and significant only for individuals with low levels of perceived social support. Results highlight the need to consider both intrapersonal and interpersonal risk factors, as well as their interaction, when predicting which individuals may be most at risk to develop depression following traumatic event exposure.

Plasticity of BRCA2 function in homologous recombination: genetic interactions of the PALB2 and DNA binding domains.

The breast cancer suppressor BRCA2 is essential for the maintenance of genomic integrity in mammalian cells through its role in DNA repair by homologous recombination (HR). Human BRCA2 is 3,418 amino acids and is comprised of multiple domains that interact with the RAD51 recombinase and other proteins as well as with DNA. To gain insight into the cellular function of BRCA2 in HR, we created fusions consisting of various BRCA2 domains and also introduced mutations into these domains to disrupt specific protein and DNA interactions. We find that a BRCA2 fusion peptide deleted for the DNA binding domain and active in HR is completely dependent on interaction with the PALB2 tumor suppressor for activity. Conversely, a BRCA2 fusion peptide deleted for the PALB2 binding domain is dependent on an intact DNA binding domain, providing a role for this conserved domain in vivo; mutagenesis suggests that both single-stranded and double-stranded DNA binding activities in the DNA binding domain are required for its activity. Given that PALB2 itself binds DNA, these results suggest alternative mechanisms to deliver RAD51 to DNA. In addition, the BRCA2 C terminus contains both RAD51-dependent and -independent activities which are essential to HR in some contexts. Finally, binding the small peptide DSS1 is essential for activity when its binding domain is present, but not when it is absent. Our results reveal functional redundancy within the BRCA2 protein and emphasize the plasticity of this large protein built for optimal HR function in mammalian cells. The occurrence of disease-causing mutations throughout BRCA2 suggests sub-optimal HR from a variety of domain modulations.

Double-strand break repair-independent role for BRCA2 in blocking stalled replication fork degradation by MRE11.

Breast cancer suppressor BRCA2 is critical for maintenance of genomic integrity and resistance to agents that damage DNA or collapse replication forks, presumably through homology-directed repair of double-strand breaks (HDR). Using single-molecule DNA fiber analysis, we show here that nascent replication tracts created before fork stalling with hydroxyurea are degraded in the absence of BRCA2 but are stable in wild-type cells. BRCA2 mutational analysis reveals that a conserved C-terminal site involved in stabilizing RAD51 filaments, but not in loading RAD51 onto DNA, is essential for this fork protection but dispensable for HDR. RAD51 filament disruption in wild-type cells phenocopies BRCA2 deficiency. BRCA2 prevents chromosomal aberrations on replication stalling, which are alleviated by inhibition of MRE11, the nuclease responsible for this form of fork instability. Thus, BRCA2 prevents rather than repairs nucleolytic lesions at stalled replication forks to maintain genomic integrity and hence likely suppresses tumorigenesis through this replication-specific function.

Control of BRCA2 cellular and clinical functions by a nuclear partner, PALB2.

BRCA2 mutations predispose carriers to breast and ovarian cancer and can also cause other cancers and Fanconi anemia. BRCA2 acts as a "caretaker" of genome integrity by enabling homologous recombination (HR)-based, error-free DNA double-strand break repair (DSBR) and intra-S phase DNA damage checkpoint control. Described here is the identification of PALB2, a BRCA2 binding protein. PALB2 colocalizes with BRCA2 in nuclear foci, promotes its localization and stability in key nuclear structures (e.g., chromatin and nuclear matrix), and enables its recombinational repair and checkpoint functions. In addition, multiple, germline BRCA2 missense mutations identified in breast cancer patients but of heretofore unknown biological/clinical consequence appear to disrupt PALB2 binding and disable BRCA2 HR/DSBR function. Thus, PALB2 licenses key cellular biochemical properties of BRCA2 and ensures its tumor suppression function.

Suppression of the DNA repair defects of BRCA2-deficient cells with heterologous protein fusions.

The BRCA2 tumor suppressor plays an important role in the repair of DNA damage by homologous recombination, also termed homology-directed repair (HDR). Human BRCA2 is 3,418 aa and is composed of several domains. The central part of the protein contains multiple copies of a motif that binds the Rad51 recombinase (the BRC repeat), and the C terminus contains domains that have structural similarity to domains in the ssDNA-binding protein replication protein A (RPA). To gain insight into the role of BRCA2 in the repair of DNA damage, we fused a single (BRC3, BRC4) or multiple BRC motifs to the large RPA subunit. Expression of any of these protein fusions in Brca2 mutant cells substantially improved HDR while suppressing mutagenic repair. A fusion containing a Rad52 ssDNA-binding domain also was active in HDR. Mutations that reduced ssDNA or Rad51 binding impaired the ability of the fusion proteins to function in HDR. The high level of spontaneous chromosomal aberrations in Brca2 mutant cells was largely suppressed by the BRC-RPA fusion proteins, supporting the notion that the primary role of BRCA2 in maintaining genomic integrity is in HDR, specifically to deliver Rad51 to ssDNA. The fusion proteins also restored Rad51 focus formation and cellular survival in response to DNA damaging agents. Because as little as 2% of BRCA2 fused to RPA is sufficient to suppress cellular defects found in Brca2-mutant mammalian cells, these results provide insight into the recently discovered diversity of BRCA2 domain structures in different organisms.

CDK-dependent phosphorylation of BRCA2 as a regulatory mechanism for recombinational repair.

Inherited mutations in BRCA2 are associated with a predisposition to early-onset breast cancers. The underlying basis of tumorigenesis is thought to be linked to defects in DNA double-strand break repair by homologous recombination. Here we show that the carboxy-terminal region of BRCA2, which interacts directly with the essential recombination protein RAD51, contains a site (serine 3291; S3291) that is phosphorylated by cyclin-dependent kinases. Phosphorylation of S3291 is low in S phase when recombination is active, but increases as cells progress towards mitosis. This modification blocks C-terminal interactions between BRCA2 and RAD51. However, DNA damage overcomes cell cycle regulation by decreasing S3291 phosphorylation and stimulating interactions with RAD51. These results indicate that S3291 phosphorylation might provide a molecular switch to regulate RAD51 recombination activity, providing new insight into why BRCA2 C-terminal deletions lead to radiation sensitivity and cancer predisposition.

Single-chain integration host factors as probes for high-precision nucleoprotein complex formation.

Integration host factor (IHF) is a heterodimeric, site-specific DNA-binding and DNA-bending protein from Escherichia coli. It is involved in high-precision DNA transactions where it serves as a key architectural component of specialized nucleoprotein structures (snups). We described recently a novel approach for protein engineering using a single polypeptide chain IHF, termed scIHF2, as a first example. ScIHF2 is made up of the alpha subunit of IHF which was inserted into the beta subunit at peptide bond Q39/G40 via two short linkers. The monomer behaves very similarly to the heterodimeric, parental IHF in biochemical and functional assays. Here, we describe an extension of this approach in which we shortened either one or both linkers by one amino acid, thereby generating three new variants termed scIHF1, 3, and 4. These variants exhibit distinct DNA-binding properties, different phenotypes in site-specific integrative and excisive recombination by phage lambda integrase in vitro, as well as in pSC101 replication assays in a DeltaIHF E. coli host. We also introduced a K45E substitution within the alpha domain of scIHF3 and based on electrophoretic mobility shift assays (EMSAs), argue that it significantly changes the DNA trajectory within the protein-DNA complex. Our results indicate that IHF's pleiotropic roles in DNA transactions inside E. coli require different types of high-precision DNA architectural activities. The scIHF variants described here will help to explore further how flexible these requirements are.

Activation of site-specific DNA integration in human cells by a single chain integration host factor.

The heterodimeric integration host factor (IHF) is a site-specific DNA-binding and DNA-bending protein from Escherichia coli. It plays essential roles in a variety of DNA transactions including recombination, transcription and DNA replication. IHF's ability for concerted binding and bending of DNA is key to its biological function. Here we report the design, characterization and application of a single polypeptide chain IHF, termed scIHF2. In a novel approach for protein engineering, we inserted almost the entire alpha-subunit of IHF into the beta-subunit. DNA binding and DNA bending assays revealed that purified wild-type IHF and scIHF2 behave very similarly. Further, scIHF2 is required for site-specific integrative recombination by phage lambda integrase and for pSC101 replication in a DeltaIHF E.coli host. It also triggers site-specific integrative and excisive recombination in vitro to the same extent as the wild-type protein. We also demonstrate that scIHF2 is stably expressed in HeLa cells, that it is localized primarily in the cell nucleus and that it triggers integrative recombination in mammalian cells by wild-type integrase. Hence, scIHF2 may be used as a novel regulatory cofactor for recombination or other DNA transactions in mammalian cells that require or benefit from sequence-specific high precision DNA bending.

Hyperphagia, not hypometabolism, causes early onset obesity in melanocortin-4 receptor knockout mice.

Previous studies on mice with melanocortin-4 receptor gene (MC4r) knockout have focused on obese adults. Because humans with functional MC4r mutations show early-onset obesity, we determined the onset of excessive fat deposition in 10- to 56-day-old mice, taking into account sex and litter influences. Total body fat content of MC4r-/- on day 35 and MC4r+/- on day 56 significantly exceeds that of MC4r+/+. Plasma leptin levels increase in proportion to fat mass. According to cumulative food intake and energy expenditure measurements from day 21 to 35, onset of excessive fat deposition in MC4r-/- is fueled by hyperphagia and counteracted partially by hypermetabolism. In 35- to 56-day-old mice, arcuate nucleus neuropeptide Y (NPY) mRNA decreases and pro-opiomelanocortin (POMC) mRNA increases with fat content and plasma leptin levels independently of genotype. Taking into account fat content by ANCOVA reveals, however, increases in both NPY mRNA and POMC mRNA due to melanocortin-4 receptor (MC4R) deficiency. We conclude that hyperphagia, not hypometabolism, is the primary disturbance initiating excessive fat deposition in MC4R-deficient mice at weaning and that the overall changes in NPY and POMC expression tend to antagonize the onset of excessive fat deposition.