How does it feel? An exploration of neurobiological and clinical correlates of alexithymia in trauma-exposed police-officers with and without PTSD

ABSTRACT

Background: Alexithymia, an inability to recognise one’s emotions, has been associated with trauma-exposure and posttraumatic stress disorder (PTSD). Previous research suggests involvement of the oxytocin system, and socio-emotional neural processes. However, the paucity of neurobiological research on alexithymia, particularly in trauma-exposed populations, warrants further investigation.

Objective: Explore associations between alexithymia, endogenous oxytocin levels, and socio-emotional brain function and morphometry in a trauma-exposed sample.

Method: Dutch trauma-exposed police officers with (n = 38; 18 females) and without PTSD (n = 40; 20 females) were included. Alexithymia was assessed with the Toronto Alexithymia Scale (TAS-20). Endogenous salivary oxytocin was assessed during rest, using radioimmunoassay. Amygdala and insula reactivity to socio-emotional stimuli were assessed with functional MRI, amygdala and insula grey matter volume were derived using Freesurfer.

Results: Alexithymia was higher in PTSD patients compared to trauma-exposed controls (F(1,70) = 54.031, p < .001). Within PTSD patients, alexithymia was positively associated with PTSD severity (ρ(36) = 0.497, p = .002). Alexithymia was not associated with childhood trauma exposure (β = 0.076, p = .509), police work-related trauma exposure (β = −0.107, p = .355), oxytocin levels (β = −0.164, p = .161), insula (β = −0.170, p = .158) or amygdala (β = −0.175, p = .135) reactivity, or amygdala volume (β = 0.146, p = .209). Insula volume was positively associated with alexithymia (β = 0.222, p = .016), though not significant after multiple testing corrections. Bayesian analyses supported a lack of associations.

Conclusions: No convincing neurobiological correlates of alexithymia were observed with any of the markers included in the current study. Yet, the current study confirmed high levels of alexithymia in PTSD patients, independent of trauma-exposure, substantiating alexithymia’s relevance in the clinical phenotype of PTSD.

HIGHLIGHTS

• Little is known about neurobiological correlates of alexithymia in trauma-exposed and posttraumatic stress disorder (PTSD) populations.

• In this highly trauma-exposed sample, alexithymia was associated with PTSD symptoms, but not with childhood or adult trauma exposure, suggesting alexithymia is not a direct consequence of trauma.

• Alexithymia was not convincingly associated with salivary oxytocin, amygdala and insula reactivity to socio-emotional stimuli, amygdala or insula grey matter volume.

Antecedentes: La alexitimia, la incapacidad para reconocer las emociones propias, se ha asociado con exposición a trauma y al trastorno de estrés postraumático (TEPT). Las investigaciones previas sugieren el compromiso del sistema de oxitocina y de procesos neuronales socioemocionales. No obstante, la escasez de estudios en la neurobiología de la alexitimia, particularmente en poblaciones expuestas a trauma, genera demanda de mayor investigación en el área.

Objetivo: Explorar las asociaciones entre la alexitimia, los niveles endógenos de oxitocina, la función socioemocional cerebral y la morfometría en una muestra expuesta a trauma.

Métodos: Se incluyó personal policial holandés expuesto a trauma con (n = 38; 18 mujeres) y sin diagnóstico de TEPT (n = 40; 20 mujeres). Se evaluó la alexitimia mediante la Escala de Alexitimia de Toronto (TAS-20) por sus siglas en inglés. Se evaluó el nivel de oxitocina endógena salival durante el descanso empleando radioinmunoensayos. La reactividad de la amígdala y de la ínsula a estímulos socioemocionales se evaluaron mediante resonancia magnética funcional (RMf) y el volumen de la sustancia gris de la amígdala y de la ínsula se obtuvo empleando Freesurfer.

Resultados: La alexitimia fue mayor en pacientes con diagnóstico de TEPT en comparación con controles expuestos a trauma sin el diagnóstico (F(1,70) = 54.031, p < .001). Dentro del grupo de pacientes con diagnóstico de TEPT, la alexitimia estaba directamente asociada con la severidad del TEPT (ρ(36) = 0.497, p = .002). La alexitimia no estaba asociada con la exposición a trauma infantil (β = 0.076, p = .509), exposición a trauma relacionada con el trabajo policial (β = −0.107, p = .355), niveles de oxitocina (β = −0.164, p = .161), reactividad de la ínsula (β = −0.170, p = .158), o reactividad de la amígdala (β = −0.175, p = .135) o el volumen de la amígdala (β = 0.146, p = .209). El volumen de la ínsula estuvo directamente asociado a la alexitimia, aunque esta asociación no fue significativa luego de múltiples correcciones de pruebas. Los análisis bayesianos respaldaban la falta de asociación.

Conclusiones: No se observaron correlaciones neurobiológicas convincentes entre la alexitimia y los marcadores incluidos en este estudio. Sin embargo, este estudio confirmó niveles altos de alexitimia en pacientes con diagnóstico de TEPT, independientemente de la exposición a trauma, fundamentando la relevancia de la alexitimia en el fenotipo clínico del TEPT.

背景：述情障碍是一种无法识别自己情绪的症状，与创伤暴露和创伤后应激障碍（PTSD）有关。先前的研究表明催产素系统和社会情绪神经过程的参与。 然而，关于述情障碍的神经生物学研究很少，特别是在遭受创伤的人群中，值得进一步研究。

目的：探索创伤暴露样本中述情障碍、内源性催产素水平以及社会情绪脑功能和形态测量之间的关联。

方法：包括患有创伤后应激障碍（n = 38；18 名女性）和未患 PTSD（n = 40；20 名女性）的创伤暴露荷兰警察。使用多伦多述情障碍量表（TAS-20）评估述情障碍。 使用放射免疫测定法在休息时评估内源性唾液催产素。通过功能性 MRI 评估杏仁核和岛叶对社会情绪刺激的反应性，并使用 Freesurfer 得出杏仁核和岛叶灰质体积。

结果：与遭受创伤的对照组相比，PTSD 患者的述情障碍更高（F(1,70) = 54.031，p < .001）。 在 PTSD 患者中，述情障碍与 PTSD 严重程度呈正相关（ρ(36) = 0.497，p = .002）。 述情障碍与童年创伤暴露（β = 0.076，p = .509）、警察工作相关创伤暴露（β = −0.107，p = .355）、催产素水平（β = −0.164，p = .161）、脑岛（β = −0.170，p = .158）或杏仁核（β = −0.175，p = .135）反应性，或杏仁核体积（β = 0.146，p = .209）无关。岛叶体积与述情障碍呈正相关（β = 0.222，p = .016），尽管经过多次测试校正后并不显著。贝叶斯分析支持缺乏关联。

结论：当前研究中的任何标记均未观察到与述情障碍有令人信服的神经生物学相关性。 然而，当前的研究证实了 PTSD 患者的述情障碍水平很高，与创伤暴露无关，证实了述情障碍与 PTSD 临床表型的相关性。

KEYWORDS:

• Alexithymia
• posttraumatic stress disorder
• trauma
• oxytocin
• amygdala
• insula

PALABRAS CLAVE:

• Alexitimia
• trastorno de estrés postraumático
• trauma
• oxitocina
• amígdala
• ínsula

关键词:

• 述情障碍
• 创伤后应激障碍
• 创伤；催产素；杏仁核；脑岛

Acknowledgements

We express our sincere gratitude to the participants of this study. We would furthermore like to thank Renée Hutter, Gré Westerveld, Marthe Hoofwijk and colleagues of the PDC police outpatient clinic for their assistance in participant recruitment and data collection; Emma Kappeyne van de Coppello for her help in the initial curation of alexithymia data; and Inga Neumann for her support regarding analyses of the salivary oxytocin assays.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Credit authorship contribution statement

Cindy van Sleeuwen: Methodology, Formal analysis, Data curation, Writing – Original Draft, Visualisation

Mirjam van Zuiden: Conceptualisation, Methodology, Writing – Review & Editing, Supervision

Saskia B.J. Koch: Investigation, Data curation, Writing – Review & Editing

Jessie L. Frijling: Investigation, Writing – Review & Editing

Dick J. Veltman: Funding acquisition, Writing – Review & Editing

Miranda Olff: Funding acquisition, Writing – Review & Editing

Laura Nawijn: Conceptualisation, Methodology, Formal analysis, Investigation, Data curation, Writing – Original Draft, Visualisation

Data availability statement

The data that support the findings of this study, and summary statistics of the dataset are available on request from the corresponding author, Laura Nawijn. The data are not publicly available due to their containment of information that could compromise the privacy of research participants.

Additional information

Funding

This study was supported by grants from the Netherlands organisation for Health research and Development [ZonMw, grant number 91210041] and from the Academic Medical Center Research Council [grant number 110614]. The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.