The effects of a multimodal intervention for optimising sleep and internalising symptoms in young adults during British Army Infantry Basic Training.

STUDY

OBJECTIVES

We assessed the effectiveness of a multimodal sleep intervention on subjective sleep outcomes, including insomnia symptoms, with secondary analysis of internalising symptoms in Infantry trainees.

METHODS

A two-arm parallel design was employed (baseline: weeks 1-3; intervention: weeks 4-12). The evidence-based intervention involved psychoeducation, sleep hygiene optimisation, pre-bedtime routines and extended sleep opportunity. Surveys were completed at training start (pre-training status), end of week-3 (baseline), and week-12 (intervention). Linear mixed models assessed the effects of time and group (participants: age 22 ± 4.9 years; control [CON], n = 40; experimental [EXP], n = 43). The CON group followed the habitual basic training sleep schedule and environment. No women enrolled in basic training during the study period.

RESULTS

Both groups experienced chronic sleep restriction, with sleep duration reduced from ~7-hours pre-training to ~5.5-hours during training, driven by earlier wake times. During the intervention, EXP shifted bedtimes ~40-minutes earlier, achieving ~30-minutes more sleep than CON and reporting significantly better sleep quality. Both groups reported increased daytime sleepiness during baseline (11.6±6.1) relative to pre-training (6.4±4.4, p<0.001) but sleepiness was significantly lower in EXP during the intervention (6.2±4.3) compared to CON (13.0±6.2, p<0.001). Controls reported significantly worse insomnia compared to EXP at pre-training (mean Δ = 2.8, p<0.01), with scores converging to subthreshold levels during baseline. EXP reported significantly less severe insomnia (4.7±2.7) compared to CON (9.1±3.7, p <0.001) during the intervention. Compared to CON, EXP reported significantly reduced stress (mean Δ -5.0, p <0.01) and clinically meaningful reductions in depressive symptoms (mean Δ -6.7 points, p<0.001) during the intervention.

CONCLUSIONS

The multimodal intervention improved insomnia and internalising symptoms. As no mental health intervention was delivered; symptom improvements likely reflect sleep-mediated effects.