Background
Little is known about the psychological mechanisms underlying the mental health problems related to the COVID-19 pandemic. Hypothetically, perceived stress and alexithymia may be factors involved in the mental distress response to the pandemic; however, this remains largely unstudied. This study aims to explore the moderating role of alexithymia and the moderated mediation effects of perceived stress on the mental health change due to the pandemic.

Methods
The conditional process model was used to examine the moderated mediation. The sample consists of 659 parents from the FinnBrain Birth Cohort Study who completed the Toronto Alexithymia Scale (TAS-20) at 6 months after delivery, the Edinburgh Postnatal Depression Scale (EPDS) and the Symptom Checklist-90 (SCL-90) at 2 or 4 years postpartum between 2014 and 2019; and a questionnaire for pandemic events, a brief 4-item version of the Perceived Stress Scale (PSS-4) and the follow-up EPDS/SCL-90 in 2020 after 3 months from the outbreak of COVID-19 pandemic in Finland.

Results
Alexithymia moderated the perceived stress-mediated relations between the pandemic events and the changes of depressive and anxiety symptoms through enhancing the detrimental effect of perceived stress on mental health.

Limitations
This study was mainly limited by the causality and generalizability of the findings.

Conclusions
Our findings indicate the moderated mediation effects of alexithymia and perceived stress on the psychological symptoms, which has implications for understanding how and when stressful situations translate to mental health problems, identifying vulnerable individuals, and tailoring preventive and psychotherapeutic interventions.