震后儿童创伤后应激障碍的症状网络演化

doi:10.3724/SP.J.1041.2020.01301

摘要/Abstract

摘要：

本研究借助网络分析方法,探讨儿童创伤后应激障碍(PTSD)症状的演化规律。以经历汶川地震的197名儿童为研究对象,在灾后4、29、40和52个月对其PTSD症状进行了历时4年的追踪测量。网络分析结果显示,闪回的中心性一直较高,而其他高中心性的症状随时间的推移发生了变化：侵入性想法和创伤线索引发生理性反应的中心性随时间推移呈上升趋势,线索引发情感反应和未来无望的中心性随时间推移呈下降趋势。本研究拓宽了学界对儿童PTSD症状学的认识, 并为建立灾后阶段性干预模式提供启示。

关键词: 创伤后应激障碍, 网络分析, 纵向研究, 发展差异, 症状学

Abstract:

Previous studies have found temporal differences in posttraumatic stress disorder (PTSD) development. Clinical workers and researchers have also demonstrated that symptoms of PTSD differ by stage after traumatic events. Recently, the symptom network perspective has contributed substantially to the development of psychopathology due to its important advantage in understanding the role of psychological symptoms in mental disorders. An increasing number of analyses adopting the network approach to study PTSD symptoms have also provided novel insights into PTSD symptomatology. However, changes in children's long-term PTSD symptomatology are poorly understood. The current study aims to identify changes in the network of PTSD symptoms among children through the network approach.
A four-year longitudinal study was conducted from 4 months after the Wenchuan earthquake. Four assessments were conducted at four (T1;September 2008), 29 (T2; October 2010), 40 (T3; September 2011) and 52 (T4; September 2012) months following the earthquake. Ultimately, 197 children completed assessments at each time point. The children were in grades four and six at T1 and attended two primary schools located in Beichuan County. Symptoms of PTSD were assessed by the University of California at Los Angeles PTSD Reaction Index based on the DSM-IV. Network analysis was implemented with the qgraph package in R following the standard guidelines by Epskamp and Fried.
Flashbacks exhibited relatively high centrality at all time points, while other symptoms with high centrality varied across time points. Emotional cue reactivity exhibited high centrality at 4 months, and its centrality decreased over time. Foreshortened future exhibited high centrality at 4, 29 and 40 months, but its centrality decreased to a low level at 52 months. Intrusive thoughts exhibited low centrality at 4 months, but the centrality of this symptom increased to a high level at 29 months. Physiological cue reactivity exhibited low centrality at 4 months, and its centrality increased over time. These findings indicated the distinct temporal variability in the centrality of some PTSD symptoms. The global connectivity of the network increased from 4 to 40 months and then decreased at 52 months.
The current study enhanced the knowledge of child PTSD symptomatology. Flashbacks might play a key role in the evolution of PTSD symptoms. In addition, different core symptoms might contribute to early and chronic PTSD structures. Emotional cue reactivity and foreshortened future might play key roles in early PTSD structures and then recover in later stages following disasters. Physiological cue reactivity and intrusive thoughts might be core symptoms in chronic PTSD structures. The phenomenon of the increased connectivity of the PTSD symptom network at 40 months may be one reason why previous trauma leads to vulnerability to PTSD. Overall, our study highlighted temporal differences in PTSD symptoms. Different core symptoms in early and chronic PTSD structures should be treated as targets at different stages following disasters in clinical practice.

Key words: posttraumatic stress symptoms, network approach, longitudinal study, developmental difference, symptomatology

中图分类号:

R395

梁一鸣, 郑昊, 刘正奎. (2020). 震后儿童创伤后应激障碍的症状网络演化. 心理学报, 52(11), 1301-1312.

LIANG Yiming, ZHENG Hao, LIU Zhengkui. (2020). Changes in the network of posttraumatic stress disorder among children after the Wenchuan earthquake: A four-year longitudinal study. Acta Psychologica Sinica, 52(11), 1301-1312.

图/表 9

图1 追踪样本详细信息

表1 被试人口学信息和创伤暴露情况

变量	频数 (百分比)
性别
男性	101 (51.27%)
女性	96 (48.73%)
年级
4年级	87 (44.16%)
6年级	110 (55.84%)
父亲受教育程度
小学及以下	79 (40.10%)
初中	68 (34.52%)
高中或中专	25 (12.69%)
大学/大专及以上	13 (6.60%)
母亲受教育程度
小学及以下	84 (42.64%)
初中	60 (30.46%)
高中或中专	26 (13.20%)
大学/大专及以上	11 (5.58%)
父母婚姻状况
原配	176 (89.34%)
离异	11 (5.58%)
再婚	5 (2.54%)
创伤暴露情况
被困	22 (11.17%)
受伤	57 (28.93%)
目睹房屋损毁	138 (70.05%)
目睹或接触尸体	104 (52.79%)
亲人去世	159 (80.71%)

图2 四个时间上的PTSD症状网络注：相同颜色的节点属于DSM-IV中同一症状簇, 彩图见电子版。 B1 = 侵入性想法, B2 = 噩梦, B3 = 闪回, B4 = 线索引发情感反应, B5 = 线索引发生理反应, C1 = 回避想法, C2 = 回避外在线索, C3 = 失忆, C4 = 兴趣减退, C5 = 与他人疏离, C6a = 积极情感受限, C6b = 消极情感受限, C7 = 对未来无望, D1 = 睡眠问题, D2 = 烦躁/愤怒, D3 = 注意力问题, D4 = 高警觉, D5 = 惊跳反应过度。

图3 PTSD在各时间点的强度中心性注：B1 = 侵入性想法, B2 = 噩梦, B3 = 闪回, B4 = 线索引发情感反应, B5 = 线索引发生理反应, C1 = 回避想法, C2 = 回避外在线索, C3 = 失忆, C4 = 兴趣减退, C5 = 与他人疏离, C6a = 积极情感受限, C6b = 消极情感受限, C7 = 对未来无望, D1 = 睡眠问题, D2 = 烦躁/愤怒, D3 = 注意力问题, D4 = 高警觉, D5 = 惊跳反应过度。

图4 PTSD各网络的子集自举结果

表2 节点强度中心性的跨时间比较

症状	M (SD) ^a				Cohen's d ^b
症状	T1	T2	T3	T4	T1 vs. T2	T2 vs. T3	T3 vs. T4	T1 vs. T4
B1	0.91 (0.18)	1.21 (0.17)	1.14 (0.15)	1.16 (0.22)	-1.73	0.44	-0.11	-1.26
B2	0.99 (0.17)	1.05 (0.15)	0.86 (0.14)	1.13 (0.27)	-0.36	1.30	-1.25	-0.61
B3	1.04 (0.17)	1.12 (0.18)	1.37 (0.1)	1.26 (0.25)	-0.46	-1.70	0.58	-1.04
B4	0.97 (0.16)	0.88 (0.13)	1.01 (0.13)	0.98 (0.26)	0.66	-1.03	0.14	-0.05
B5	0.79 (0.14)	0.9 (0.13)	1.08 (0.12)	1.27 (0.28)	-0.75	-1.44	-0.89	-2.17
C1	0.76 (0.18)	0.7 (0.14)	0.72 (0.12)	0.87( 0.28)	0.35	-0.08	-0.71	-0.47
C2	0.72 (0.17)	1.00 (0.14)	1.04 (0.12)	1.24 (0.27)	-1.79	-0.31	-0.96	-2.29
C3	0.66 (0.18)	0.7 (0.17)	0.84 (0.18)	0.87 (0.27)	-0.24	-0.79	-0.11	-0.91
C4	0.96 (0.14)	1.09 (0.17)	1.03 (0.14)	1.25 (0.24)	-0.87	0.39	-1.12	-1.50
C5	1.01 (0.15)	1.18 (0.17)	1.15 (0.12)	1.11 (0.25)	-1.06	0.21	0.21	-0.49
C6a	0.73 (0.16)	1.01 (0.15)	0.96 (0.13)	1.24 (0.31)	-1.78	0.34	-1.18	-2.08
C6b	0.45 (0.15)	0.41 (0.18)	0.55 (0.16)	0.75 (0.27)	0.22	-0.83	-0.86	-1.34
C7	1.00 (0.19)	1.09 (0.17)	1.13 (0.12)	1.20 (0.38)	-0.50	-0.27	-0.25	-0.66
D1	0.82 (0.16)	0.87 (0.16)	0.96 (0.14)	1.02 (0.16)	-0.29	-0.61	-0.42	-1.24
D2	0.85 (0.17)	1.01 (0.14)	0.9 (0.14)	1.11 (0.28)	-1.05	0.76	-0.93	-1.13
D3	0.80 (0.16)	0.75 (0.18)	0.71 (0.13)	0.88 (0.19)	0.27	0.27	-1.05	-0.45
D4	0.72 (0.18)	0.86 (0.19)	0.82 (0.17)	1.12 (0.38)	-0.76	0.21	-1.01	-1.34
D5	0.92 (0.15)	0.83 (0.17)	0.93 (0.12)	0.87 (0.20)	0.55	-0.71	0.37	0.25

附图S1 四次网络估计中接近度和中介性指标估计结果(a: 4个月, b: 29个月, c: 40个月, d: 52个月) 注：B1 = 侵入性想法, B2 = 噩梦, B3 = 闪回, B4 = 线索引发情感反应, B5 = 线索引发生理反应, C1 = 回避想法, C2 = 回避外在线索, C3 = 失忆, C4 = 兴趣减退, C5 = 与他人疏离, C6a = 积极情感受限, C6b = 消极情感受限, C7 = 对未来无望, D1 = 睡眠问题, D2 = 烦躁/愤怒, D3 = 注意力问题, D4 = 高警觉, D5 = 惊跳反应过度。

附图S2 四次PTSD网络中边缘权重的自举置信区间(CI) (a: 4个月, b: 29个月, c: 40个月, d: 52个月) 注：红线表示边缘权重值, 灰色区域表示95% CI。

附图S3 四次调查中PTSD症状网络的节点强度中心性差异测试 (a: 4个月, b: 29个月, c: 40个月, d: 52个月) 注：黑框表示两个节点间存在显著差异(α= 0.05)。 B1 = 侵入性想法, B2 = 噩梦, B3 = 闪回, B4 = 线索引发情感反应, B5 = 线索引发生理反应, C1 = 回避想法, C2 = 回避外在线索, C3 = 失忆, C4 = 兴趣减退, C5 = 与他人疏离, C6a = 积极情感受限, C6b = 消极情感受限, C7 = 对未来无望, D1 = 睡眠问题, D2 = 烦躁/愤怒, D3 = 注意力问题, D4 = 高警觉, D5 = 惊跳反应过度。

参考文献 55

[1]	American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders, 5th ed. Washington, DC: American Psychiatric Association.
[2]	Armour, C., Fried E. I., Deserno M. K., Tsai, J., & Pietrzak R. H.(2017). A network analysis of DSM-5 posttraumatic stress disorder symptoms and correlates in U.S. military veterans. Journal of Anxiety Disorders, 45, 49-59.
[3]	Bartels, L., Berliner, L., Holt, T., Jensen, T., Jungbluth, N., Plener, P.,... Sachser, C.(2019). The importance of the DSM‐5 posttraumatic stress disorder symptoms of cognitions and mood in traumatized children and adolescents: Two network approaches. Journal of Child Psychology and Psychiatry, 60(5), 545-554. URL pmid: 30648742
[4]	Benfer, N., Bardeen, J. R., Cero, I., Kramer, L. B., Whiteman, S. E., Rogers, T. A., ... Weathers, F. W.(2018). Network models of posttraumatic stress symptoms across trauma types. Journal of Anxiety Disorders, 58, 70-77. URL pmid: 30055470
[5]	Birkeland, M. S., Greene, T., & Spiller, T. R.(2020). The network approach to posttraumatic stress disorder: A systematic review. European Journal of Psychotraumatology, 11(1), 1700614. doi: 10.1080/20008198.2019.1700614 URL pmid: 32002135
[6]	Borsboom, D.(2017). A network theory of mental disorders. World Psychiatry, 16(1), 5-13. URL pmid: 28127906
[7]	Borsboom, D., & Cramer, A. O. J.(2013). Network analysis: An integrative approach to the structure of psychopathology. Annual Review of Clinical Psychology, 9, 91-121. URL pmid: 23537483
[8]	Braun-Lewensohn, O.(2015). Coping and social support in children exposed to mass trauma. Current Psychiatry Reports, 17, 1-10. doi: 10.1007/s11920-014-0542-0 URL pmid: 25617038
[9]	Bryant R. A., Creamer, M., O'Donnell, M., Forbes, D., McFarlane, A. C., Silove, D., & Hadzi-Pavlovic, D.(2017). Acute and chronic posttraumatic stress symptoms in the emergence of posttraumatic stress disorder: A network analysis. JAMA Psychiatry, 74(2), 135-142. URL pmid: 28002832
[10]	Cao, X., Wang, L., Cao, C., Fang, R., Chen, C., Hall, B. J., & Elhai, J. D.(2019). Sex differences in global and local connectivity of adolescent posttraumatic stress disorder symptoms. Journal of Child Psychology and Psychiatry, 60(2), 216-224. URL pmid: 30125943
[11]	Chen, X., Wang, R., & Liu, Z.(2009). Organization and implementation of psychological interventions after major disaster. Advances in Psychological Science, 17(3), 499-504.
	[ 陈雪峰, 王日出, 刘正奎.(2009). 灾后心理援助的组织与实施. 心理科学进展, 17(3), 499-504.]
[12]	Cheng, J., Liang Y. M., Zhou, Y. Y., Eli, B., & Liu, Z. K.(2019). Trajectories of PTSD symptoms among children who survived the Lushan earthquake: A four-year longitudinal study. Journal of Affective Disorders, 252, 421-427. URL pmid: 31003111
[13]	Cohen, J.(1988). Statistical power analysis for the behavioral sciences (2nd ed.). Lawrence Erlbaum Associates, Hillsdale, NJ.
[14]	Cramer, A. O., Waldorp, L. J., van der Maas H. L., & Borsboom, D. (2010). Complex realities require complex theories: Refining and extending the network approach to mental disorders. Behavioral and Brain Sciences, 33(2-3), 178-193.
[15]	de Haan, A., Landolt, M. A., Fried, E. I., Kleinke, K., Alisic, E., Bryant, R., ... Meiser-Stedman, R.(2020). Dysfunctional posttraumatic cognitions, posttraumatic stress and depression in children and adolescents exposed to trauma: A network analysis. Journal of Child Psychology and Psychiatry, 61(1), 77-87. URL pmid: 31701532
[16]	Epskamp, S., & Fried, E. I.(2018). A tutorial on regularized partial correlation networks. Psychological Methods, 23(4), 617-634. doi: 10.1037/met0000167 URL pmid: 29595293
[17]	Epskamp, S., Borsboom, D., & Fried, E. I.(2018). Estimating psychological networks and their accuracy: A tutorial paper. Behavior Research Methods, 50, 195-212. URL pmid: 28342071
[18]	Epskamp, S., Cramer, A. O., Waldorp, L. J., Schmittmann, V. D., & Borsboom, D. (2012). qgraph: Network visualizations of relationships in psychometric data. Journal of Statistical Software, 48(4), 1-18.
[19]	Fan, F., Long, K., Zhou, Y., Zheng, Y., & Liu, X. (2015). Longitudinal trajectories of post-traumatic stress disorder symptoms among adolescents after the Wenchuan earthquake in China. Psychological Medicine, 45(13), 2885-2896. URL pmid: 25990926
[20]	Fruchterman, T. M., & Reingold, E. M.(1991). Graph drawing by force-directed placement. Software: Practice and Experience, 21(11), 1129-1164.
[21]	Galatzer-Levy, I. R., Huang, S. H., & Bonanno, G. A.(2018). Trajectories of resilience and dysfunction following potential trauma: A review and statistical evaluation. Clinical Psychology Review, 63, 41-55. URL pmid: 29902711
[22]	Ge, F., Yuan, M., Li, Y., Zhang, J., & Zhang, W. (2019). Changes in the network structure of posttraumatic stress disorder symptoms at different time points among youth survivors: A network analysis. Journal of Affective Disorders, 259, 288-295. URL pmid: 31454591
[23]	Guo, J., He, H., Qu, Z., Wang, X., & Liu, C. (2017). Post-traumatic stress disorder and depression among adult survivors 8 years after the 2008 Wenchuan earthquake in China. Journal of Affective Disorders, 210, 27-34. URL pmid: 28006696
[24]	Helpman, L., Rachamim, L., Aderka, I. M., Gabai-Daie, A., Schindel-Allon, I., & Gilboa-Schechtman, E. (2015). Posttraumatic symptom structure across age groups. Journal of Clinical Child and Adolescent Psychology, 44(4), 630-639.
[25]	Hofstra, M. B., van der Ende J., & Verhulst, F. C.(2002). Child and adolescent problems predict DSM-IV disorders in adulthood: A 14-year follow-up of a Dutch epidemiological sample. Journal of the American Academy of Child & Adolescent Psychiatry, 41(2), 182-189. doi: 10.1097/00004583-200202000-00012 URL pmid: 11837408
[26]	Keane, T. M., Marshall, A. D., & Taft, C. T.(2006). Posttraumatic stress disorder: Etiology, epidemiology, and treatment outcome. Annual Review of Clinical Psychology, 2, 161-197. URL pmid: 17716068
[27]	Kelley, L. P., Weathers, F. W., McDevitt-Murphy, M. E., Eakin, D. E., & Flood, A. M.(2009). A comparison of PTSD symptom patterns in three types of civilian trauma. Journal of Traumatic Stress, 22(3), 227-235.
[28]	Lai, B. S., Lewis, R., Livings, M. S., La Greca A. M., & Esnard, A. M.(2017). Posttraumatic stress symptom trajectories among children after disaster exposure: A review. Journal of Traumatic Stress, 30(6), 571-582.
[29]	Levy-Gigi, E., Richter-Levin, G., Okon-Singer, H., Keri, S., & Bonanno, G. A.(2016). The hidden price and possible benefit of repeated traumatic exposure. Stress, 19(1), 1-7. doi: 10.3109/10253890.2015.1113523 URL pmid: 26513400
[30]	Liang, Y., Cheng, J., Ruzek, J., & Liu, Z. (2019). Posttraumatic stress disorder following the 2008 Wenchuan earthquake: A 10-year systematic review among highly exposed populations in China. Journal of Affective Disorder, 243, 327-339.
[31]	Liang, Y., Cheng, J., Zhou, Y., & Liu, Z. (2019). Trajectories of posttraumatic stress disorders among children after the Wenchuan earthquake: A four-year longitudinal study. European Journal of Psychotraumatology, 10(1), 1586266. URL pmid: 30911361
[32]	Liang, Y., Zhou, Y., & Liu, Z. (2019). Traumatic experiences and posttraumatic stress disorder among Chinese rural-to-urban migrant children. Journal of Affective Disorders, 257, 123-129. URL pmid: 31301612
[33]	Liu, H., Petukhova, M. V., Sampson, N. A., Aguilar-Gaxiola, S., Alonso, J., Andrade, L. H., ... Kawakami, N.(2017). Association of DSM-IV posttraumatic stress disorder with traumatic experience type and history in the world health organization world mental health surveys. JAMA Psychiatry, 74(3), 270-281. doi: 10.1001/jamapsychiatry.2016.3783 URL pmid: 28055082
[34]	Liu, Z., Liu, Y., & Wang, R.(2017). Crisis intervention and psychological assistance after sudden man-made disasters. Bulletin of Chinese Academy of Sciences, 32(2), 166-174.
	[ 刘正奎, 刘悦, 王日出.(2017). 突发人为灾难后的心理危机干预与援助. 中国科学院院刊, 32(2), 166-174.]
[35]	Liu, Z., Liu, Y., Zhang, Y., Chen, Z., & Hannak, W. J.(2014). Developing a Chinese PTSD Inventory (CPI) based on interviews with earthquake victims in Sichuan. Psych Journal, 3(2), 101-112. URL pmid: 26272761
[36]	McLaughlin, K. A., Koenen, K. C., Hill, E. D., Petukhova, M., Sampson, N. A., Zaslavsky, A. M., & Kessler, R. C.(2013). Trauma exposure and posttraumatic stress disorder in a national sample of adolescents. Journal of the American Academy of Child & Adolescent Psychiatry, 52(8), 815-830. doi: 10.1016/j.jaac.2013.05.011 URL pmid: 23880492
[37]	McNally, R. J.(2016). Can network analysis transform psychopathology? Behaviour Research and Therapy, 86, 95-104. doi: 10.1016/j.brat.2016.06.006 URL pmid: 27424882
[38]	McNally, R. J., Robinaugh, D. J., Wu, G. W., Wang, L., Deserno, M. K., & Borsboom, D.(2015). Mental disorders as causal systems: A network approach to posttraumatic stress disorder. Clinical Psychological Science, 3(6), 836-849.
[39]	McNally, R. J.(2017). Networks and nosology in posttraumatic stress disorder. JAMA Psychiatry, 74, 124-125. URL pmid: 27973667
[40]	Moshier, S. J., Bovin, M. J., Gay, N. G., Wisco, B. E., Mitchell, K. S., Lee, D. J., … Keane, T. M.(2018). Examination of posttraumatic stress disorder symptom networks using clinician-rated and patient-rated data. Journal of Abnormal Psychology, 127, 541-547. URL pmid: 30102064
[41]	Neigh, G. N., & Ali, F. F.(2016). Co-morbidity of PTSD and immune system dysfunction: Opportunities for treatment. Current Opinion in Pharmacology, 29, 104-110. doi: 10.1016/j.coph.2016.07.011 URL pmid: 27479489
[42]	Opsahl, T., Agneessens, F., & Skvoretz, J.(2010). Node centrality in weighted networks: Generalizing degree and shortest paths. Social Networks, 32(3), 245-251.
[43]	Osofsky, J. D., Osofsky, H. J., Weems, C. F., King, L. S., & Hansel, T. C.(2015). Trajectories of post-traumatic stress disorder symptoms among youth exposed to both natural and technological disasters. Journal of Child Psychology and Psychiatry, 56(12), 1347-1355. doi: 10.1111/jcpp.12420 URL
[44]	Pacella, M. L., Hruska, B., & Delahanty, D. L.(2013). The physical health consequences of PTSD and PTSD symptoms: A meta-analytic review. Journal of Anxiety Disorders, 27(1), 33-46. doi: 10.1016/j.janxdis.2012.08.004 URL pmid: 23247200
[45]	Phillips, R. D., Wilson, S. M., Sun, D., Workgroup, V. M. A. M., & Morey, R.(2018). Posttraumatic stress disorder symptom network analysis in U.S. Military Veterans: Examining the impact of combat exposure. Frontiers in Psychiatry, 9, 608. doi: 10.3389/fpsyt.2018.00608 URL pmid: 30519198
[46]	Robinaugh, D. J., Hoekstra, R. H.A., Toner, E. R., Borsboom, D. (2020). The network approach to psychopathology: A review of the literature 2008-2018 and an agenda for future research. Psychological Medicine, 50(3), 353-366. URL pmid: 31875792
[47]	Rodriguez, N., Steinberg, A. M., Saltzman, W. S., & Pynoos, R. S.(2001a). Youth PTSD Assessment: Psychometric investigation of PTSD self-report instruments. In 17th Annual ISTSS Meeting, New Orleans.
[48]	Rodriguez, N., Steinberg, A. S., Saltzman, W. S., & Pynoos, R. S.(2001b). PTSD Index: Psychometric analyses of the adolescent version. In Symposium conducted at the annual meeting of the International Society for Traumatic Stress Studies, New Orleans, LA.
[49]	Ross, J., Murphy, D., & Armour, C.(2018). A network analysis of DSM-5 posttraumatic stress disorder and functional impairment in UK treatment-seeking veterans. Journal of Anxiety Disorders, 57, 7-15. URL pmid: 29886306
[50]	Russell, J. D., Neill, E. L., Carrion, V. G., & Weems, C. F.(2017). The network structure of posttraumatic stress symptoms in children and adolescents exposed to disasters. Journal of the American Academy of Child and Adolescent Psychiatry, 56(8), 669-677. URL pmid: 28735696
[51]	Steinberg, A. M., Brymer, M. J., Decker, K. B., & Pynoos, R. S.(2004). The University of California at Los Angeles post-traumatic stress disorder reaction index. Current Psychiatry Reports, 6, 96-100.
[52]	Tibshirani, R.(1996). Regression shrinkage and selection via the lasso. Journal of the Royal Statistical Society Series B (Methodological), 58(1), 267-288.
[53]	van Borkulo C. D., Borsboom, D., Epskamp, S., Blanken, T. F., Boschloo, L., Schoevers, R. A., & Waldorp, L. J.(2014). A new method for constructing networks from binary data. Scientific Reports, 4, 5918. doi: 10.1038/srep05918 URL pmid: 25082149
[54]	van Borkulo C. D., Boschloo, L., Kossakowski, J., Tio, P., L., Schoevers, R. A., Borsboom, D., & Waldorp, L. J.(2016). Comparing network structures on three aspects: A permutation test. ( Preprint). doi: 10.13140/RG.2.2.29455. 38569
[55]	von Stockert, S. H., Fried, E. I., Armour, C., & Pietrzak, R. H.(2018). Evaluating the stability of DSM-5 PTSD symptom network structure in a national sample of U.S. military veterans. Journal of Affective Disorders, 229, 63-68.