maternal deprivation

Summary

Summary: Prolonged separation of the offspring from the mother.

Top Publications

  1. Huang T, Lin C. A comparison between chronic exercise training and desipramine as treatments for the depression-like behavior of early-life maternal deprivation rats. Neurosci Lett. 2010;480:201-5 pubmed publisher
    We have established a depression-like behavioral animal model through maternal deprivation in rats during early life...
  2. Li M, Xue X, Shao S, Shao F, Wang W. Cognitive, emotional and neurochemical effects of repeated maternal separation in adolescent rats. Brain Res. 2013;1518:82-90 pubmed publisher
    ..These data further demonstrate that MS can be used as an animal model of neuropsychiatric disease. ..
  3. Monroy E, Hernández Torres E, Flores G. Maternal separation disrupts dendritic morphology of neurons in prefrontal cortex, hippocampus, and nucleus accumbens in male rat offspring. J Chem Neuroanat. 2010;40:93-101 pubmed publisher
    ..These anatomical modifications may be relevant to altered behaviors observed in maternally separated animals. ..
  4. Oreland S, Pickering C, Gokturk C, Oreland L, Arborelius L, Nylander I. Two repeated maternal separation procedures differentially affect brain 5-hydroxytryptamine transporter and receptors in young and adult male and female rats. Brain Res. 2009;1305 Suppl:S37-49 pubmed publisher
    ..The results suggest that MS15i is less suitable than MS15l to simulate a protective environment in studies of, for instance, ethanol addiction processes. ..
  5. Faturi C, Tiba P, Kawakami S, Catallani B, Kerstens M, Suchecki D. Disruptions of the mother-infant relationship and stress-related behaviours: altered corticosterone secretion does not explain everything. Neurosci Biobehav Rev. 2010;34:821-34 pubmed publisher
    ..Based on a series of studies, we propose that maternal separation and maternal deprivation change stress-related behaviours, but that corticosterone seem to be only partially involved in these ..
  6. Mourlon V, Baudin A, Blanc O, Lauber A, Giros B, Naudon L, et al. Maternal deprivation induces depressive-like behaviours only in female rats. Behav Brain Res. 2010;213:278-87 pubmed publisher
    b>Maternal deprivation (MD) has been developed to study the effects of early adverse experiences on behaviour and neurobiology. It has been proposed to represent a potential animal model of major depression...
  7. Maniam J, Morris M. Long-term postpartum anxiety and depression-like behavior in mother rats subjected to maternal separation are ameliorated by palatable high fat diet. Behav Brain Res. 2010;208:72-9 pubmed publisher
    ..Moreover, they support the notion of long-term beneficial effects of 'comfort food' on stress responses. ..
  8. Xu H, Hu W, Zhang X, Gao W, Liang M, Chen T, et al. The effect of different maternal deprivation paradigms on the expression of hippocampal glucocorticoid receptors, calretinin and calbindin-D28k in male and female adolescent rats. Neurochem Int. 2011;59:847-52 pubmed publisher
    b>Maternal deprivation (MD) is a well-established protocol used to investigate neurobiological changes that are associated with the etiology of and vulnerability to stress-related diseases in animal models...
  9. Martini M, Valverde O. A single episode of maternal deprivation impairs the motivation for cocaine in adolescent mice. Psychopharmacology (Berl). 2012;219:149-58 pubmed publisher
    Early-life adverse events, like maternal deprivation (MD), have been associated with the later development of mood and anxiety disorders...

Scientific Experts

More Information

Publications62

  1. Uysal N, Sisman A, Dayi A, Aksu I, Cetin F, Gencoglu C, et al. Maternal exercise decreases maternal deprivation induced anxiety of pups and correlates to increased prefrontal cortex BDNF and VEGF. Neurosci Lett. 2011;505:273-8 pubmed publisher
    b>Maternal deprivation (MD) may cause neuropsychiatric disorders such as anxiety disorder by negatively affecting the cognitive functions and behavior in pups...
  2. Franklin T, Russig H, Weiss I, Graff J, Linder N, Michalon A, et al. Epigenetic transmission of the impact of early stress across generations. Biol Psychiatry. 2010;68:408-15 pubmed publisher
    ..These findings highlight the negative impact of early stress on behavioral responses across generations and on the regulation of DNA methylation in the germline. ..
  3. Réus G, Stringari R, Ribeiro K, Cipriano A, Panizzutti B, Stertz L, et al. Maternal deprivation induces depressive-like behaviour and alters neurotrophin levels in the rat brain. Neurochem Res. 2011;36:460-6 pubmed publisher
    The present study was aimed to evaluate the behavioral and molecular effects of maternal deprivation in adult rats. To this aim, male rats deprived and non-deprived were assessed in the forced swimming and open-field tests in adult phase...
  4. Luo J, Qin H, Wong C, Tsang S, Huang Y, Bian Z. Enhanced excitability and down-regulated voltage-gated potassium channels in colonic drg neurons from neonatal maternal separation rats. J Pain. 2011;12:600-9 pubmed publisher
    ..2 expression in DRG neurons from IBS model rats, representing a molecular mechanism underlying visceral pain and sensitization in IBS, suggesting the potential of Kv1.2 as a therapeutic target for the treatment of IBS. ..
  5. Callaghan B, Richardson R. Maternal separation results in early emergence of adult-like fear and extinction learning in infant rats. Behav Neurosci. 2011;125:20-8 pubmed publisher
    ..Taken together, these results suggest that early life adversity may prepare young animals to respond more cautiously toward fear signals in their environment. ..
  6. Aisa B, Gil Bea F, Marcos B, Tordera R, Lasheras B, Del Rio J, et al. Neonatal stress affects vulnerability of cholinergic neurons and cognition in the rat: involvement of the HPA axis. Psychoneuroendocrinology. 2009;34:1495-505 pubmed publisher
    ..The present data are discussed not only in terms of conditions that occur during ageing or Alzheimer disease, but also regarding a purported involvement of the cholinergic system in the regulation of HPA axis activity. ..
  7. Martisova E, Solas M, Horrillo I, Ortega J, Meana J, Tordera R, et al. Long lasting effects of early-life stress on glutamatergic/GABAergic circuitry in the rat hippocampus. Neuropharmacology. 2012;62:1944-53 pubmed publisher
    ..Modulation of glutamate/GABA release may be a relevant component of the therapeutic action of antidepressants, such as venlafaxine. ..
  8. Takase K, Yamamoto Y, Yagami T. Maternal deprivation in the middle of a stress hyporesponsive period decreases hippocampal calcineurin expression and causes abnormal social and cognitive behaviours in adult male Wistar rats: relevance to negative symptoms of schizophrenia. Behav Brain Res. 2012;232:306-15 pubmed publisher
    ..Numerous studies have provided evidence that maternal deprivation in the middle of a stress hyporesponsive period (SHRP) causes multiple behavioural and physiological ..
  9. Romano López A, Méndez Díaz M, Ruiz Contreras A, Carrisoza R, Prospero Garcia O. Maternal separation and proclivity for ethanol intake: a potential role of the endocannabinoid system in rats. Neuroscience. 2012;223:296-304 pubmed publisher
    ..These findings suggest that MS induces changes in the CB1R expression, which might contribute to induce a proclivity to ingest alcohol and, potentially, other drugs. ..
  10. Réus G, Abelaira H, Dos Santos M, Carlessi A, Tomaz D, Neotti M, et al. Ketamine and imipramine in the nucleus accumbens regulate histone deacetylation induced by maternal deprivation and are critical for associated behaviors. Behav Brain Res. 2013;256:451-6 pubmed publisher
  11. Bian Z, Zhang M, Han Q, Xu H, Sung J. Analgesic effects of JCM-16021 on neonatal maternal separation-induced visceral pain in rats. World J Gastroenterol. 2010;16:837-45 pubmed
    ..01-0.001). JCM-16021 can attenuate visceral hypersensitivity, and this analgesic effect may be mediated through the serotonin signaling pathway in the colon of rats. ..
  12. Stevenson C, Spicer C, Mason R, Marsden C. Early life programming of fear conditioning and extinction in adult male rats. Behav Brain Res. 2009;205:505-10 pubmed publisher
    ..They also indicate that different early rearing conditions can program varying effects on distinct fear learning and memory processes in adulthood. ..
  13. van Heerden J, Russell V, Korff A, Stein D, Illing N. Evaluating the behavioural consequences of early maternal separation in adult C57BL/6 mice; the importance of time. Behav Brain Res. 2010;207:332-42 pubmed publisher
    ..The extension of conventional analysis strategies, to include time as a significant dimension of behaviour on the EPM, identified behavioural nuances, which could reflect adaptive aspects of stress-driven behaviours in MS mice. ..
  14. Daoura L, Haaker J, Nylander I. Early environmental factors differentially affect voluntary ethanol consumption in adolescent and adult male rats. Alcohol Clin Exp Res. 2011;35:506-15 pubmed publisher
    ..Further studies are now warranted to examine the consequences of a combination of early environmental influence and high adolescent ethanol intake. ..
  15. Oreland S, Gustafsson Ericson L, Nylander I. Short- and long-term consequences of different early environmental conditions on central immunoreactive oxytocin and arginine vasopressin levels in male rats. Neuropeptides. 2010;44:391-8 pubmed publisher
    ..We propose that environmentally induced alterations in OT transmission due to disrupted mother-pup interactions early in life may cause altered susceptibility to challenges later in life. ..
  16. Chocyk A, Przyborowska A, Dudys D, Majcher I, Mackowiak M, Wedzony K. The impact of maternal separation on the number of tyrosine hydroxylase-expressing midbrain neurons during different stages of ontogenesis. Neuroscience. 2011;182:43-61 pubmed publisher
  17. Lievajová K, Blasko J, Martončíková M, Cigankova V, Racekova E. Delayed maturation and altered proliferation within the rat rostral migratory stream following maternal deprivation. Eur J Histochem. 2011;55:e33 pubmed publisher
    ..To induce stress, the pups were subjected to repeated maternal deprivation during the first postnatal week after birth. Brains were analyzed at the seventh postnatal day...
  18. Litvin Y, Tovote P, Pentkowski N, Zeyda T, King L, Vasconcellos A, et al. Maternal separation modulates short-term behavioral and physiological indices of the stress response. Horm Behav. 2010;58:241-9 pubmed publisher
    ..These findings may have direct relevance for understanding the mechanisms by which early-life adverse experiences produce short-term and lasting psychopathologies. ..
  19. Aaron L, Dallaire D. Parental incarceration and multiple risk experiences: effects on family dynamics and children's delinquency. J Youth Adolesc. 2010;39:1471-84 pubmed publisher
    ..The role of family processes in research and intervention directions involving children of incarcerated parents is discussed. ..
  20. Hulshof H, Novati A, Sgoifo A, Luiten P, den Boer J, Meerlo P. Maternal separation decreases adult hippocampal cell proliferation and impairs cognitive performance but has little effect on stress sensitivity and anxiety in adult Wistar rats. Behav Brain Res. 2011;216:552-60 pubmed publisher
    ..In conclusion, while interfering with the mother-infant relationship early in life did affect some aspects of adult neuroplasticity and cognitive function, it did not lead to permanent changes in stress sensitivity and emotionality. ..
  21. Viveros M, Llorente R, Diaz F, Romero Zerbo S, Bermudez Silva F, Rodriguez de Fonseca F, et al. Maternal deprivation has sexually dimorphic long-term effects on hypothalamic cell-turnover, body weight and circulating hormone levels. Horm Behav. 2010;58:808-19 pubmed publisher
    b>Maternal deprivation (MD) has numerous outcomes, including modulation of neuroendocrine functions...
  22. Réus G, Dos Santos M, Abelaira H, Ribeiro K, Petronilho F, Vuolo F, et al. Imipramine reverses alterations in cytokines and BDNF levels induced by maternal deprivation in adult rats. Behav Brain Res. 2013;242:40-6 pubmed publisher
    ..05). Interestingly, imipramine treatment reversed the effects of maternal deprivation on BDNF and cytokines levels (p<0.05)...
  23. Lajud N, Roque A, Cajero M, Gutiérrez Ospina G, Torner L. Periodic maternal separation decreases hippocampal neurogenesis without affecting basal corticosterone during the stress hyporesponsive period, but alters HPA axis and coping behavior in adulthood. Psychoneuroendocrinology. 2012;37:410-20 pubmed publisher
    ..The data show that the decrease in hippocampal neurogenesis is an early onset phenomenon, and suggests that adverse experiences alter hippocampal ontogeny without chronic elevation of GC levels. ..
  24. Leussis M, Freund N, Brenhouse H, Thompson B, Andersen S. Depressive-like behavior in adolescents after maternal separation: sex differences, controllability, and GABA. Dev Neurosci. 2012;34:210-7 pubmed
    ..Understanding the risk factors for depression, the nature of depressive-like behaviors, and their unique sex dependency may ultimately provide insight into improved treatments. ..
  25. Chen J, Evans A, Liu Y, Honda M, Saavedra J, Aguilera G. Maternal deprivation in rats is associated with corticotrophin-releasing hormone (CRH) promoter hypomethylation and enhances CRH transcriptional responses to stress in adulthood. J Neuroendocrinol. 2012;24:1055-64 pubmed publisher
    ..in the CRH promoter leading to increased CRH transcription, 8-week old female and male rats, subjected to maternal deprivation (MD) between days 2 and 13 post-birth, were studied for HPA axis responses to stress and CRH promoter ..
  26. Wei L, Simen A, Mane S, Kaffman A. Early life stress inhibits expression of a novel innate immune pathway in the developing hippocampus. Neuropsychopharmacology. 2012;37:567-80 pubmed publisher
  27. Gee D, Gabard Durnam L, Flannery J, Goff B, Humphreys K, Telzer E, et al. Early developmental emergence of human amygdala-prefrontal connectivity after maternal deprivation. Proc Natl Acad Sci U S A. 2013;110:15638-43 pubmed publisher
    ..Rodent models show that maternal deprivation accelerates this development, prompting examination of human amygdala-mPFC phenotypes following maternal ..
  28. Viveros M, Diaz F, Mateos B, Rodríguez N, Chowen J. Maternal deprivation induces a rapid decline in circulating leptin levels and sexually dimorphic modifications in hypothalamic trophic factors and cell turnover. Horm Behav. 2010;57:405-14 pubmed publisher
    Pathological outcomes, including metabolic and endocrine disturbances, of maternal deprivation (MD) in Wistar rats depend on gender and the timing of deprivation during development...
  29. Aksić M, Radonjić N, Aleksić D, Jevtić G, Marković B, Petronijević N, et al. Long-term effects of the maternal deprivation on the volume and number of neurons in the rat neocortex and hippocampus. Acta Neurobiol Exp (Wars). 2013;73:394-403 pubmed
    b>Maternal deprivation (MD) leads to a variety of behavioral changes in rats which closely resemble the symptoms of schizophrenia in humans...
  30. Daskalakis N, Claessens S, Laboyrie J, Enthoven L, Oitzl M, Champagne D, et al. The newborn rat's stress system readily habituates to repeated and prolonged maternal separation, while continuing to respond to stressors in context dependent fashion. Horm Behav. 2011;60:165-76 pubmed publisher
    ..In conclusion, separation environment, maternal care and genotype do not affect adrenal desensitization to repeated 8 h-MS itself, but may modulate the adrenal stress-responsiveness of separated pups. ..
  31. Suarez J, Rivera P, Llorente R, Romero Zerbo S, Bermudez Silva F, de Fonseca F, et al. Early maternal deprivation induces changes on the expression of 2-AG biosynthesis and degradation enzymes in neonatal rat hippocampus. Brain Res. 2010;1349:162-73 pubmed publisher
    Early maternal deprivation (MD) in rats (24h, PND 9-10) is a model for neurodevelopmental stress...
  32. Oomen C, Soeters H, Audureau N, Vermunt L, van Hasselt F, Manders E, et al. Severe early life stress hampers spatial learning and neurogenesis, but improves hippocampal synaptic plasticity and emotional learning under high-stress conditions in adulthood. J Neurosci. 2010;30:6635-45 pubmed publisher
    ..e., 24 h of maternal deprivation (MD), a model for maternal neglect...
  33. Oreland S, Raudkivi K, Oreland L, Harro J, Arborelius L, Nylander I. Ethanol-induced effects on the dopamine and serotonin systems in adult Wistar rats are dependent on early-life experiences. Brain Res. 2011;1405:57-68 pubmed publisher
    ..These altered responses to initial ethanol consumption as a result of early environmental factors may affect the transition from habitual to compulsive drinking and contribute to individual vulnerability or resilience to addiction. ..
  34. Sterley T, Howells F, Russell V. Effects of early life trauma are dependent on genetic predisposition: a rat study. Behav Brain Funct. 2011;7:11 pubmed publisher
    ..Basal levels of corticosterone correlate with the behavioural response to early life trauma, and may therefore provide a useful marker for susceptibility to a certain behavioural temperament. ..
  35. Benetti F, Da Silveira C, da Silva W, Cammarota M, Izquierdo I. Histamine reverses a memory deficit induced in rats by early postnatal maternal deprivation. Neurobiol Learn Mem. 2012;97:54-8 pubmed publisher
    Early partial maternal deprivation causes long-lasting neurochemical, behavioral and brain structural effects. In rats, it causes a deficit in memory consolidation visible in adult life...
  36. Oomen C, Soeters H, Audureau N, Vermunt L, van Hasselt F, Manders E, et al. Early maternal deprivation affects dentate gyrus structure and emotional learning in adult female rats. Psychopharmacology (Berl). 2011;214:249-60 pubmed publisher
    ..We studied whether 24 h of maternal deprivation (MD) on postnatal day 3 altered adult neurogenesis, individual neuronal morphology and dentate gyrus (DG) ..
  37. Mello P, Benetti F, Cammarota M, Izquierdo I. Physical exercise can reverse the deficit in fear memory induced by maternal deprivation. Neurobiol Learn Mem. 2009;92:364-9 pubmed publisher
    b>Maternal deprivation during the first 10 days of life induces significant behavioral alterations in rodents which persist through adulthood...
  38. Zhang Y, Zhu X, Bai M, Zhang L, Xue L, Yi J. Maternal deprivation enhances behavioral vulnerability to stress associated with miR-504 expression in nucleus accumbens of rats. PLoS ONE. 2013;8:e69934 pubmed publisher
    In this study, the effect of maternal deprivation (MD) and chronic unpredictable stress (CUS) in inducing depressive behaviors and associated molecular mechanism were investigated in rats...
  39. van Den Wijngaard R, Klooker T, Welting O, Stanisor O, Wouters M, van der Coelen D, et al. Essential role for TRPV1 in stress-induced (mast cell-dependent) colonic hypersensitivity in maternally separated rats. Neurogastroenterol Motil. 2009;21:1107-e94 pubmed publisher
    ..Moreover, the results also suggest that TRPV1 modulation (in the absence of overt inflammation) is involved in this response. Thus, mast cells and TRPV1 are potential targets to treat stress-induced visceral hypersensitivity. ..
  40. Li L, Xie R, Hu S, Wang Y, Yu T, Xiao Y, et al. Upregulation of cystathionine beta-synthetase expression by nuclear factor-kappa B activation contributes to visceral hypersensitivity in adult rats with neonatal maternal deprivation. Mol Pain. 2012;8:89 pubmed publisher
    ..CVH was induced by neonatal maternal deprivation (NMD) in male rats on postnatal days 2-15 and behavioral experiments were conducted at the age of 7-15 ..
  41. Rodenas Ruano A, Chavez A, Cossio M, Castillo P, Zukin R. REST-dependent epigenetic remodeling promotes the developmental switch in synaptic NMDA receptors. Nat Neurosci. 2012;15:1382-90 pubmed publisher
    ..Knockdown of REST in vivo prevented the decline in GluN2B and developmental switch in NMDARs. Maternal deprivation impaired REST activation and acquisition of the mature NMDAR phenotype...
  42. Der Avakian A, Markou A. Neonatal maternal separation exacerbates the reward-enhancing effect of acute amphetamine administration and the anhedonic effect of repeated social defeat in adult rats. Neuroscience. 2010;170:1189-98 pubmed publisher
    ..Thus, early life stress may increase an individual's vulnerability to depressive or addictive disorders when confronted with stress or drug challenge in adulthood. ..
  43. Uchida S, Hara K, Kobayashi A, Funato H, Hobara T, Otsuki K, et al. Early life stress enhances behavioral vulnerability to stress through the activation of REST4-mediated gene transcription in the medial prefrontal cortex of rodents. J Neurosci. 2010;30:15007-18 pubmed publisher
    ..These results suggest that the activation of REST4-mediated gene regulation in the mPFC during postnatal development is involved in stress vulnerability. ..
  44. Llorente R, Miguel Blanco C, Aisa B, Lachize S, Borcel E, Meijer O, et al. Long term sex-dependent psychoneuroendocrine effects of maternal deprivation and juvenile unpredictable stress in rats. J Neuroendocrinol. 2011;23:329-44 pubmed publisher
    We have analysed the long-term psychoneuroendocrine effects of maternal deprivation (MD) [24 h at postnatal day (PND) 9] and/or exposure to chronic unpredictable stress (CUS) during the periadolescent period (PND 28 to PND 43) in male and ..
  45. Solas M, Aisa B, Mugueta M, Del Rio J, Tordera R, Ramirez M. Interactions between age, stress and insulin on cognition: implications for Alzheimer's disease. Neuropsychopharmacology. 2010;35:1664-73 pubmed publisher
    ..The present results may provide the proof-of-concept for the use of glucocorticoid-/insulin-related drugs in the treatment of AD. ..
  46. Zhu X, Li T, Peng S, Ma X, Chen X, Zhang X. Maternal deprivation-caused behavioral abnormalities in adult rats relate to a non-methylation-regulated D2 receptor levels in the nucleus accumbens. Behav Brain Res. 2010;209:281-8 pubmed publisher
    In this study we investigated the effects of maternal deprivation on adult rats' spatial learning and memory, exploratory, and limbic activity and their correlations with the gene expression of dopamine transporter (DAT) and dopamine D1, ..
  47. Maniam J, Morris M. Palatable cafeteria diet ameliorates anxiety and depression-like symptoms following an adverse early environment. Psychoneuroendocrinology. 2010;35:717-28 pubmed publisher
    ..These results highlight the important place of palatable food in reducing central stress responses supporting the therapeutic value of 'comfort food'. ..
  48. Levine A, Worrell T, Zimnisky R, Schmauss C. Early life stress triggers sustained changes in histone deacetylase expression and histone H4 modifications that alter responsiveness to adolescent antidepressant treatment. Neurobiol Dis. 2012;45:488-98 pubmed publisher
    ..These results suggest that Balb/c mice develop epigenetic modifications after early life stress exposure that, in terms of the emotive phenotype, are of adaptive nature, and that enhance the efficacy of antidepressant drugs. ..
  49. Benekareddy M, Goodfellow N, Lambe E, Vaidya V. Enhanced function of prefrontal serotonin 5-HT(2) receptors in a rat model of psychiatric vulnerability. J Neurosci. 2010;30:12138-50 pubmed publisher
    ..Together, our results demonstrate enhanced prefrontal 5-HT(2) receptor function and persistent alterations in prefrontal gene expression in a rat model of psychiatric vulnerability. ..
  50. Mela V, Llorente Berzal A, Diaz F, Argente J, Viveros M, Chowen J. Maternal deprivation exacerbates the response to a high fat diet in a sexually dimorphic manner. PLoS ONE. 2012;7:e48915 pubmed publisher
    b>Maternal deprivation (MD) during neonatal life has diverse long-term effects, including affectation of metabolism...
  51. Pautassi R, Nizhnikov M, Fabio M, Spear N. Early maternal separation affects ethanol-induced conditioning in a nor-BNI insensitive manner, but does not alter ethanol-induced locomotor activity. Pharmacol Biochem Behav. 2012;100:630-8 pubmed publisher
    ..These results indicate that, when assessed in infant rats, earlier maternal separation alters the balance between the appetitive and aversive motivational effects of ethanol but has no effect on the motor activating effects of the drug. ..
  52. López Gallardo M, López Rodríguez A, Llorente Berzal A, Rotllant D, Mackie K, Armario A, et al. Maternal deprivation and adolescent cannabinoid exposure impact hippocampal astrocytes, CB1 receptors and brain-derived neurotrophic factor in a sexually dimorphic fashion. Neuroscience. 2012;204:90-103 pubmed publisher
    We have recently reported that early maternal deprivation (MD) for 24 h [postnatal day (PND) 9-10] and/or an adolescent chronic treatment with the cannabinoid agonist CP-55,940 (CP) [0...
  53. Csoka S, Simor P, Szabo G, Kopp M, Bodizs R. Early maternal separation, nightmares, and bad dreams: results from the Hungarostudy Epidemiological Panel. Attach Hum Dev. 2011;13:125-40 pubmed publisher
    ..This enhancement influences the content of dreams and, when it takes the form of depression, also influences the frequency of nightmares...