YEHUDA 2005 NEUROPEPT Y TRAUMA EXP RECOVERY PTSD COPING

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Plasma Neuropeptide Y Concentrations in Combat Exposed Veterans: Relationship to Trauma Exposure, Recovery from PTSD, and Coping Rachel Yehuda, Sarah Brand, and Ren-Kui Yang Background: There is emerging interest in examining the role of plasma neuropeptide Y (NPY) as a protective stress factor. Methods: To further investigate this possibility, plasma NPY was measured in 11 nonexposed veterans, 11 combat-exposed veterans without posttraumatic stress disorder (PTSD), and 12 veterans with current PTSD. Results: A significant group difference in plasma NPY (F2,31 ⫽ 5.16, p ⫽ .012) was observed, reflecting higher NPY levels in exposed veterans without PTSD than in nonexposed but comparable levels in veterans with current PTSD. Among those without current PTSD, veterans with past PTSD had higher NPY levels than those without past PTSD (t9 ⫽ 2.71, p ⫽ .024). After controlling for all other variables, NPY levels were significantly predicted by extent of symptom improvement and lower combat exposure and significant at a trend level with positive coping. Conclusions: Plasma NPY levels may represent a biologic correlate of resilience to or recovery from the adverse effects of stress.

Key Words: Coping, neuropeptide Y, neurotransmitters, posttraumatic stress disorder, resilience

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he release of neuropeptide Y (NPY) is thought to facilitate the containment of negative consequences following exposure to stress (Heilig 2004). Evidence for this idea includes anxiolytic actions and impairing effects on stress-induced memory retention following microinjection of NPY to the amygdale of rats (Flood et al 1989; Heilig et al 1989), increased emotionality to stress in transgenically altered rats in which the NPY gene is knocked out, and decreased behavioral responses when the NPY gene is overexpressed (Thorsell et al 2000). Significantly higher plasma NPY levels were observed in soldiers subjected to the “uncontrollable stress” of interrogation, which produced extreme subjective psychological distress and clinically significant dissociation (Morgan et al 2000); however, NPY was subsequently found to correlate with feelings of dominance and confidence during stress, which in turn was associated with superior performance as assessed by the interrogators (Morgan et al 2002). Lower NPY levels have been observed in posttraumatic stress disorder (PTSD) (Rasmusson et al 2000) and depressive disorder (Heilig et al 2004); correspondingly, antidepressant drugs increase NPY levels (Mathe 2002). To further examine whether plasma NPY levels in PTSD are related to protective stress factors, we measured this peptide in non-combat-exposed and exposed veterans without PTSD, and veterans with PTSD, hypothesizing that NPY levels would be highest among exposed veterans without PTSD and lowest in PTSD. We also determined the relative contributions of combat exposure, severity of PTSD and depression, PTSD remission, and coping to the prediction of NPY levels.

Methods and Materials Participants Thirty-four male veterans provided written informed consent to participate in this study, approved by the Internal Review From the Traumatic Stress Studies Program, Psychiatry Department, Mount Sinai School of Medicine, and the Bronx Veterans Affairs Medical Center, New York, New York. Address reprint requests to Rachel Yehuda, Ph.D., Bronx VA OOMH,130 West Kingsbridge Road, Bronx, NY 10468; E-mail: [email protected].

0006-3223/06/$32.00 doi:10.1016/j.biopsych.2005.08.027

Boards of Mount Sinai School of Medicine and the Bronx Veterans Affairs Medical Center. Participants underwent a medical exam with laboratory tests to confirm the absence of medical illness. Three subjects were taking stable doses of psychotropics. Participants were evaluated with the Clinician Administered PTSD Scale (CAPS; Blake et al 1995) and the Structured Clinical Interview for DSM-IV (Spitzer et al 1995). Subjects were included in the PTSD-positive (PTSD⫹) group if they met the diagnostic criteria for current PTSD, but not other Axis I disorders except depression or anxiety disorder; in the PTSD-negative (PTSD⫺) group if exposed to a military trauma and were without current Axis I disorder; and in the nonexposed group if unexposed to military trauma and without Axis I disorder. Participants completed the Combat Exposure Scale (Keane et al 1989), the Beck Depression Inventory (Beck et al 1961), and the COPE scale (Carver 1989). Biological Assessments Blood was drawn by venipuncture at approximately 8 A.M. and plasma NPY determined by radioimmunoassay using reagents purchased from ALPCO Diagnostics (Windham, New Hampshire). Briefly, 200 ␮L of plasma were mixed with 200 ␮L of anti-NPY serum, and duplicate samples were incubated at 4°C for 18 –24 hours; 200 ␮L of 125I-NPY was added and incubated at 4°C for 18 –24 hours, and 100 ␮L of second antibody solid-phase was added and kept at room temperature for 30 – 60 min. The tubes were centrifuged at 4°C for 20 min, and the precipitate counted by ICN APEX automatic gamma counter for 4 min. Cross-reactions of the anti-NPY serum with peptide-YY was ⬍2.0%, with pancreatic polypeptide, ⬍1.0%, with NPY 1–21, ⬍.1% and with NPY 20 –36, ⬍.4%. The detection limit was 6 pmol/L. The intra- and interassay variations were 3.3% and 11.6%, respectively. Statistical Analyses Group differences were determined by analysis of variance (ANOVA) followed by Bonferroni post hoc testing. Correlates of NPY were determined using linear regression analysis.

Results The three groups did not differ in age, height, weight, systolic blood pressure, or positive coping but did differ in diastolic BIOL PSYCHIATRY 2006;59:660 – 663 © 2005 Society of Biological Psychiatry

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Table 1. Demographic and Psychological Data on the Three Groups of Veterans with and Without PTSD

Age Height Weight Systolic Blood Pressure Diastolic Blood Pressure NPY (pmol/L) Combat Exposure CAPS Current CAPS Lifetime Symptom Improvement Positive Coping Negative Coping

Non–Combat Exposed (n ⫽ 11)

PTSD⫹ (n ⫽ 12)

PTSD⫺ (n ⫽ 11)

F (p) df ⫽ 2,31

64.00 ⫾ 9.46 69.64 ⫾ 1.91 188.10 ⫾ 41.86 147.18 ⫾ 22.60 86.73 ⫾ 11.28 73.61 ⫾ 29.47 .18 ⫾ .60 .55 ⫾ 1.81 2.90 ⫾ 8.06 2.36 ⫾ 6.26 71.13 ⫾ 17.11 37.88 ⫾ 6.58

60.42 ⫾ 7.53 69.21 ⫾ 6.16 193.33 ⫾ 35.29 131.87 ⫾ 9.68 80.56 ⫾ 7.45 94.37 ⫾ 30.41 20.36 ⫾ 17.23 59.58 ⫾ 14.09 86.33 ⫾ 29.11 26.75 ⫾ 21.32 73.00 ⫾ 13.36 47.5 ⫾ 8.99

63.55 ⫾ 9.37 67.82 ⫾ 2.75 171.19 ⫾ 27.31 134.70 ⫾ 16.32 75.20 ⫾ 5.75 109.80 ⫾ 17.18 13.09 ⫾ 14.71 8.82 ⫾ 7.55 30.09 ⫾ 29.11 21.27 ⫾ 24.65 71.20 ⫾ 13.29 38.10 ⫾ 3.67

.57 (ns) .50 (ns) 1.21 (ns) 2.26 (ns) 4.69 (.018)a 5.16 (.012)a 6.71 (.004)b 132.24 (.001)c 49.90 (.001)d 4.58 (.018)b .06 (ns) 6.56 (.005)c

CAPS, Clinician Administered PTSD Scale; Delta CAPS, Lifetime CAPS score minus Current CAPS score; Positive Coping include subscales for positive reinterpretation and growth, active coping, planning, seeking social support for emotional and instrumental reasons, religion, and acceptance. Negative Coping included subscales for behavioral disengagement, mental disengagement, denial, restraint coping, and alcohol or drug use. Coping and combat exposure are missing for one participant who did not feel comfortable disclosing the information. Blood pressure is missing for four participants. PTSD, posttraumatic stress disorder. a Bonferroni post hoc testing revealed significant differences between the nonexposed and PTSD⫺ group. b Bonferroni post hoc testing revealed significant differences between the nonexposed and PTSD⫹ group. c Bonferroni post hoc testing revealed significant differences between the nonexposed and PTSD⫹ group as well as the PTSD⫺ and PTSD⫹ group. d Bonferroni Post hoc testing revealed significant differences between the nonexposed and PTSD⫺ group, the nonexposed and the PTSD⫹ group, and the PTSD⫹ and PTSD⫺ group.

blood pressure, combat exposure, PTSD and depression severity, PTSD symptom improvement (CAPS lifetime—CAPS current), and negative coping (Table 1). Post hoc testing confirmed that the PTSD⫹ group was significantly more combat-exposed and symptomatic than the other groups. A significant group difference in plasma NPY (F2,31 ⫽ 5.16; p ⫽ .012) was observed reflecting that the PTSD⫺ group had higher NPY levels than nonexposed veterans (p ⫽ .010) but not those with PTSD. Table 2 shows that when the PTSD⫺ group was subdivided based on presence or absence of past PTSD, the Table 2. Demographic and Psychological Data for the Subgroup of Veterans with and Without Past PTSD, but not current PTSD Past PTSD (n ⫽ 5) Age Height Weight Systolic Blood Pressure Diastolic Blood Pressure NPY (pmol/L) Combat Exposure CAPS Current CAPS Lifetime Symptom Change Positive Coping Negative Coping

No Past PTSD (n ⫽ 6)

t(p) df ⫽ 9

61.00 ⫾ 6.52 65.67 ⫾ 11.40 .81 (ns) 66.80 ⫾ 3.83 68.67 ⫾ 1.21 1.14 (ns) 181.20 ⫾ 38.35 162.83 ⫾ 11.44 1.13 (ns) 135.25 ⫾ 11.21 135.00 ⫾ 20.10 .07 (ns) 77.50 ⫾ 5.80 73.67 ⫾ 5.68 ⫺1.04 (ns) 121.82 ⫾ 13.54 99.78 ⫾ 13.36 2.71 (.024) 21.00 ⫾ 17.07 8.33 ⫾ 9.27 1.57 (ns) 13.40 ⫾ 8.36 5.00 ⫾ 4.43 2.14 (.061) 58.60 ⫾ 14.50 6.33 ⫾ 6.06 8.09 (.001) 45.20 ⫾ 14.06 1.33 ⫾ 2.80 7.54 (.001) 71.60 ⫾ 16.62 70.80 ⫾ 10.99 .41 (ns) 38.60 ⫾ 4.22 37.60 ⫾ 3.44 .09 (ns)

CAPS, Clinician Administered PTSD Scale; Delta CAPS, Lifetime CAPS score minus Current CAPS score; Positive Coping include subscales for positive reinterpretation and growth, active coping, planning, seeking social support for emotional and instrumental reasons, religion, and acceptance. Negative Coping included subscales for behavioral disengagement, mental disengagement, denial, restraint coping, and alcohol or drug use. Coping, combat exposure, and blood pressure are missing data for one participant who did not feel comfortable disclosing the information. PTSD, posttraumatic stress disorder.

former (121.82 ⫾ 13.53 pmol/L) had significantly higher NPY levels (t9 ⫽ 2.71, p ⫽ .024) than the latter (99.77 ⫾ 13.35 pmol/L). The subgroups also differed in current and lifetime PTSD severity and improvement but not in combat exposure and coping. When subjects were grouped based on presence or absence of any (current or lifetime) PTSD, NPY levels were higher in the 17 subjects with (102.44 ⫾ 29.12), compared to 17 subjects without (82.84 ⫾ 27.63), PTSD (F1,33 ⫽ 4.05; p ⫽ .053). When considering the contribution of all measures associated with symptom severity, trauma exposure, symptom improvement, and coping in the prediction of NPY, a significant model was generated (R2 ⫽ .409; F5,22 ⫽ 3.05; p ⫽ .031); however, when controlling for each of the other variables, NPY was associated significantly with extent of symptom improvement and lower combat exposure, at a trend level significance with positive coping, and not at all with severity of PTSD or depression (Table 3).

Discussion An association between NPY and resistance to, or recovery from, adverse effects of stress is demonstrated by greater NPY Table 3. Linear Regression of NPY and Psychological Predictors Variables Current PTSD Severity Total Combat Exposure Current Depression Severity Positive Coping Symptom Improvement

Zero-Order Correlation

Partial Correlation

Beta

.112 .030 .030 .310 .447ⴱ

.117 ⫺.438ⴱ .030 .367 .566ⴱ

.111 ⫺.517ⴱ .113 .306 .689ⴱ

Significance for zero-order correlations are based on two-tailed tests. Positive Coping includes subscales for positive reinterpretation and growth, active coping, planning, seeking social support for emotional and instrumental reasons, religion, and acceptance. PTSD, posttraumatic stress disorder. ⴱp ⬍ .05.

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662 BIOL PSYCHIATRY 2006;59:660 – 663 concentrations in trauma-exposed veterans without PTSD compared with veterans with PTSD and in those showing a greater diminution of symptoms. That no differences in NPY levels were observed between subjects with current PTSD and the other groups contradicts a previous observation of reduced NPY levels in combat veterans with PTSD compared with eight significantly younger control subjects (Rasmusson et al 2000) but is consistent with another report by the same authors showing no differences in combat veterans with PTSD compared with combat veterans without PTSD and nonexposed subjects (Morgan et al 2003) and with lack of difference in NPY levels in PTSD in women exposed to domestic violence compared with nonexposed control subjects (Seedat et al 2003). If anything, NPY levels seemed higher in relation to PTSD, particularly when considering differences in this peptide between subjects with and without lifetime PTSD; however, when regression analysis was performed to determine the relative contributions of several dimensions associated with trauma exposure and PTSD after controlling for the effects of all others, the strongest predictor of NPY was symptom improvement. Regression analysis also demonstrated that NPY levels were negatively correlated with combat exposure and showed a trend for a positive association with coping. Although NPY was found to be lower in combat-exposed persons compared with nonexposed persons (Morgan et al 2003), in our study, the simple correlation between NPY and combat exposure was not significant without considering this relationship in the context of symptom severity and recovery. The association between NPY levels and positive coping may help explain the lack of observed differences in relation to PTSD. Because subjects with current PTSD did not differ from other groups on positive coping, they would not be expected to have lower NPY levels if NPY levels are related to a behavioral mediator of stress. The lack of difference in positive coping suggests either that this trait does not guarantee PTSD remission or that symptomatic subjects may overendorse positive coping traits. Yet negative coping traits were significantly higher in those with current PTSD. That exposed subjects with and without PTSD were not significantly different on improvement in PTSD symptoms, also associated with NPY levels, reflects that the subgroup of veterans without PTSD were relatively less symptomatic to begin with, in part due possibly to their lower combat exposure. Rather, the subgroup with past PTSD, showing the most dramatic improvement in PTSD, also showed highest levels of NPY. That there are stress-related peptides associated with protection in the face of demands imposed by acute or chronic stress is consistent with initial conceptions that emphasized the role of stress hormones in facilitating and containing defensive responses to stress (Munck et al 1984; Selye 1955). Because stress exposure is associated with so many negative outcomes, including mental and physical illness, it has, however, been difficult to differentiate between the biological responses that are associated with protection versus damage. This difficulty is compounded by the fact that biological responses resulting from the continued demands of chronic stressors or the cumulative burden (i.e., allostatic load) of subsequent stress exposure may have very different effects from the same responses occurring in the absence of cumulative burden (McEwen 2004). Furthermore, the actions of any single stress-related neuropeptide are diverse and can even seem contradictory. For example, injection of NPY in brain both increases corticotropin levels (Small et al 1997) and decreases norepinephrine (NE) in the locus coeruleus (Illes et al www.sobp.org/journal

R. Yehuda et al 1993). NPY enhances NE-mediated vasoconstriction (Han et al 1998) but, when injected centrally, reduces arterial blood pressure and heart tone (Morton et al 1999). Thus, in the absence of knowledge about the diverse actions of stress-related peptide and without clear criteria on which to make determinations about protective versus damaging effects, caution must be applied in the interpretation of hormone or neuropeptide levels or identifying specific alterations in response to stress as the basis of a target for pharmacologic intervention. Nonetheless, that NPY levels may constitute a biologic correlate of a potential behavioral mediator of stress such as positive coping provides an observation that warrants further research. Given the relative ease of measuring plasma NPY levels, it is appropriate to consider adding such assessments to biologic studies of trauma and PTSD. This work was supported by a VA Merit Review Grant (RY), and, in part, by a grant (Grant No. 5 M01 RR00071) for the Mount Sinai General Clinical Research Center from the National Institute of Health. We thank Dr. Julia Golier for providing medical clearance, Dr. Lisa Tischler for supervision of diagnostic assessments and consensus conferences, Dr. Linda Bierer for helpful comments on the manuscript, and Karina Stavitsky for coordinating this study. Beck AT, Ward CH, Mendelson M, Mock J, Erbaugh J (1961): An inventory for measuring depression. Arch Gen Psychiatry 4:561–590. Blake DD, Weathers FW, Nagy LM, Kaloupek DG, Gusman FD, Charney DS et al (1995): The development of a Clinician-Administered PTSD Scale. J Trauma Stress 8:75–90. Carver CS, Scheier MF, Weintraub JK (1989): Assessing coping strategies: A theoretically based approach. J Pers Soc Psychol 56:267–283. Flood JF, Baker ML, Hernande WN, Morley JE (1989): Modulation of memory processing by neurpeptide Y varies with brain injection site. Brain Res 503:73– 82. Han S, Yang CL, Chen X, Nacs L, Cox B, Westfall T (1998): Direct evidence for the role of neuropeptide Y in sympathetic nerve stimulation-induced vasoconstriction. Am J Physiol 274: H290 –H294. Heilig M (2004): The NPY system in stress, anxiety and depression. Neuropeptides 38:213–224. Heilig M, Soderpalm B, Engel J, Widerlov E (1989): Centrally administered neuropeptide Y produces anxiolytic-lide effects in animal anxiety models. Psychopharmocology 98:524 –529. Heilig M, Zachrisson O, Thorsell A, Ehnvall A, Mottagui-Tabar S, Sjogren M, et al (2004): Decreased cerebrospinal fluid neuropeptide Y (NPY) in patients with treatment refractory unipolar major depression: preliminary evidence for association with prepro NPY gene polymorphism. J Psychiatr Res 38:113–12. Illes P, Finta EP, Nieber K (1993): Neuropeptide T potentiates via Y-2 receptors the inhibitory effect of noradrenaline in rat locus coeruleus neurons. Naunyn Scmiedebergs Arch Pharmacol 348:546 –548. Keane T, Fairbank J, Caddell J, Zimering R, Taylor K, Mora C (1989): Clinical evaluation of a measure to assess combat exposure. Psychol Assess 1:53–55. Mathe HH (2002): Early life stress changes concentrations of neuropeptide Y and CRH in adult rat brain: lithium treatment modifies these changes. Neuropsychopharmacology 27:756 –764. McEwen BS (2004): Protection and damage from acute and chronic stress. Ann N Y Acad Sci 1032:1–7. Morgan CA 3rd, Rasmusson AM, Wang S, Hoyt G, Hauger RL, Hazlett G (2002) Neuropeptide-Y, cortisol, and subjective distress in humans exposed to acute stress: replication and extension of previous report. Biol Psychiatry 52:136 –142. Morgan CA 3rd, Rasmusson AM, Winters B, Hauger RL, Morgan J, Hazlett G, Southwick S (2003): Trauma exposure rather than posttraumatic stress disorder is associated with reduced baseline plasma neuropeptide-Y levels. Biol Psychiatry 54:1087–1091. Morgan CA 3rd, Wang S, Southwick SM, Rasmusson A, Hazlett G, Hauger RL, Charney DS (2000): Plasma neuropeptide-Y concentrations in humans exposed to military survival training. Biol Psychiatry 47:902–909.

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