Restless legs syndrome is common in pregnancy, but a new study highlighted by the American Academy of Sleep Medicine finds that timing matters for a consequence many clinicians may not be watching for: when the condition shows up late in pregnancy, it appears to carry a substantially higher risk of perinatal depression.
A Large Cohort, Tracked Across Trimesters
The research, led by Tezuka and colleagues and published in the Journal of Clinical Sleep Medicine, drew on data from 2,435 Japanese pregnant women who had been enrolled as the control group of a randomized controlled trial originally designed to study perinatal depression. That structure gave researchers an unusually well-characterized population to look back through for restless legs syndrome symptoms at two distinct points in pregnancy.
Restless legs syndrome — a neurological condition that produces an uncomfortable, often irresistible urge to move the legs, typically worse in the evening and at rest — turned out to be present in a relatively small share of the group: 40 women (1.6%) in the second trimester and 60 women (3.5%) in the third trimester. Both figures are lower than some previous estimates of RLS prevalence in pregnancy, which the study's authors note as a limitation of self-reported, questionnaire-based identification.
The Trimester Mattered
The key finding was not simply that RLS was linked to depression, but that the timing of its onset changed the picture entirely. Women whose restless legs syndrome was identified in the third trimester had roughly triple the risk of developing perinatal depression compared with women without the condition. Women whose RLS was identified earlier, in the second trimester, showed no significant increase in depression risk at all.
That split pattern echoes, but also complicates, earlier research. A 2014 study in the same journal found that women with RLS onset before pregnancy, and with moderate-to-severe symptoms, had an increased risk of both antenatal and postnatal depression, while women with RLS arising fresh during pregnancy showed no significant association. Taken together, the two studies suggest that it isn't restless legs syndrome in general driving the depression link — it's specific patterns of timing and severity that matter, and researchers still don't have a clean, unified explanation for why.
One plausible mechanism is sleep disruption itself. RLS symptoms characteristically worsen in the evening and interfere with falling and staying asleep, and third-trimester sleep is already compromised by physical discomfort, more frequent urination, and anxiety about approaching labor. Stacking a movement disorder onto an already fragile sleep window late in pregnancy may tip some women toward clinically significant depressive symptoms in a way that earlier-pregnancy RLS, met with more sleep reserve, does not.
Limitations the Researchers Flagged
The study's authors were candid about its constraints. Beyond the lower-than-expected prevalence of RLS in the sample, the number of women who had both RLS and depression was small, which limits statistical precision. Participants were self-selected volunteers in a clinical trial, which may not represent the broader population of pregnant women, and both RLS symptoms and depression were assessed through self-report rather than clinical diagnosis. The authors also note that their data cannot establish whether treating RLS would lower a woman's depression risk — that question requires a dedicated intervention trial.
What This Means for Patients
For pregnant women experiencing new or worsening restless legs symptoms in their third trimester, this study is a reason to mention it to an obstetric provider rather than dismiss it as a routine late-pregnancy discomfort. Screening for mood symptoms alongside RLS in the final trimester, rather than treating the two as unrelated complaints, may help identify women at elevated risk for perinatal depression earlier — potentially opening the door to sleep-focused interventions, iron status checks (low iron is a well-established RLS trigger), or closer mental health monitoring heading into the postpartum period. The findings don't yet prove that fixing RLS prevents depression, but they strengthen the case for treating the two as connected rather than coincidental.
