This study provides sensitive, fully interpretable models and comprehensive analysis of the child malnutrition seasonality in Yemen guided by the acute malnutrition conceptual framework [23]. We reflect on the findings from three vantage points: 1–recognizing the seasonal synchronization of malnutrition patterns across space; 2–recognizing the synchronization of seasonal patterns (or the lack of) in malnutrition drivers, indicating internal temporal sequences and time lags across environmental indicators, food prices, coping strategies, and food insecurity; 3–recognizing the implications of synchronization for understanding the evolution of malnutrition and famine.

Spatial synchronization. Our analysis detects a significant seasonal pattern of malnutrition across most governorates in Yemen, with the majority exhibiting a single annual peak occurring between late July and early October, which aligns with the lean season [35]. We also observed some discrepancies where southern Yemen has a higher percentage of people with insufficient food but a lower percentage of people using crisis or above-crisis-level food coping strategies compared to the north. Higher food insufficiency in southern Yemen could be associated with the food price gap between south and north Yemen, with north Yemen having higher food prices [36]. However, humanitarian aid and more effective local coping mechanisms, such as community aid programs and remittances, may play a more significant role in mitigating the need for extreme coping strategies. In contrast, in northern Yemen, conflict and logistical challenges may limit access to aid. Reports indicate that the Houthis’ systematic obstruction of aid agencies, combined with a collapse in donor funding [30], has compounded the situation, forcing more people to resort to severe, crisis-level coping strategies.

Temporal synchronization. Within regions, the results reveal relatively consistent seasonal patterns in the timing of environmental factors, prices, coping strategies, food insecurity, humanitarian assistance, and malnutrition over time. Temporal synchonization could suggests potential sequences with short time lags. For example, challenging environmental indicators couls lead to price increases and more severe coping strategies that only temporarily protect against a rise in food insecurity and then malnutrition. Humanitarian assistance attempts to alleviate this seasonal rise. There are several points to explore further.

First, the syncronized peak timing between admissions for treatment of children with SAM and screenings of acute malnutrition from different organizations (OCHA/UNICEF and WHO) carries several important implications. This synchronization might indicate that humanitarian assistance and monitoring systems are effectively capturing the same seasonal peaks in malnutrition, presenting an opportunity for earlier interventions to prevent SAM through more coordinated, integrated, and timely interventions across organizations. In general, by ensuring resources are mobilized before critical periods when SAM rates will be at their highest, these efforts can improve the efficiency of response measures, reduce duplication, and enhance the overall impact of humanitarian assistance on malnutrition. Additionally, it suggests that aligning and integrating surveillance and treatment data could allow for more accurate forecasting and early warning systems [37], enabling preemptive actions that prevent further deterioration in child health during peak malnutrition seasons. The close alignment of seasonal patterns between food insecurity and acute child malnutrition supports the notion that food availability and household food security are critical underlying drivers of malnutrition in Yemen. Similar time series analyses conducted in Tanzania [38] and Malawi [39] also found a significant seasonal association between child malnutrition and food insecurity, further supporting this connection among vulnerable populations across African and South Asian countries.

Second, the strong seasonal patterns and their temporal alignment to malnutrition in environmental indicators, particularly NDVI, underscore their influence on malnutrition and food security in Yemen. A study conducted among dryland African countries found that NDVI most correlate with child acute malnutrition compared to other environmental factors like precipitation and temperature [20]. The synchronization between NDVI peaks and malnutrition outcomes in both regions in our study could be explained by the alignment of humanitarian aid and health campaigns with periods of highest malnutrition risk, leading to increased screening and treatment during the peak in vegetation; on the other hand, households may be more likely to bring their children to health centers for screening at the end of the planting season. The northern region, with its more intense rainfall and earlier NDVI peak values, experiences an earlier peak in malnutrition. This finding aligns with studies in sub-Saharan African countries, which have demonstrated a positive association between climate factors—such as rainfall and vegetation patterns—and the prevalence of acute malnutrition [40, 41], likely due to the more rapid depletion of food resources post-harvest.

Third, while conflict events did not exhibit a strong seasonal pattern, they remain a critical factor exacerbating food insecurity and malnutrition in Yemen. In our analysis, secondary peaks in food insecurity coincided with the peak of conflict-related events in governorates such as Hajjah, Ibb, Sa’ada, Aden, and Shabwah. This aligns with findings from other studies, which demonstrate that conflict was positively and statistically associated with the increase in child wasting [10, 42]. However, the absence of a clear seasonal pattern for conflict suggests that its impact is unpredictable, creating challenges for designing timely interventions.

Implications for famine modeling. The key contribution of these findings lay in recognizing the implications of seasonal synchronization for understanding the evolution of malnutrition and famine. An emerging theory of famine formation [26, 43] suggests that these crises arise when pressure (a combination of shocks and vulnerability) is kept in place by a hold (something such as access constraints that prevents release from pressure) leading to self-reinforcing dynamics (a linked set of changes resulting in food insecurity and undernutrition) that tip over into a famine system (a rapid rise in hunger-related mortality) before rebalancing (a return to the baseline mortality). The spatial and temporal patterns that have been discussed contribute specifically to explaining the synchronized sequences that occur as the pressure leads to self-reinforcing dynamics. That is, for these contexts, it provides evidence of a pattern in which the pressure, or the environmental factors, trigger self-reinforcing dynamics, or sequential changes in prices and coping strategies leading, with a time lag, to rises in food insecurity and then malnutrition. This pattern, therefore, sheds light on and makes visible these complex interactions. It also allows us to see that, in this case, the delay in humanitarian assistance constitutes a hold.

In addition to the description of the Yemen case, the findings suggest three broader directions for exploring these components of famine evolution and modeling famine dynamics. First, in our early work, we proposed methodology to detect three forms of synchronization: 1–serial synchronization that captures whether two or more outcomes (or locations) share a similar temporal pattern; 2–phase-phase synchronization that derives associations between peak timing estimates and identifies co-occurrences in timing of two or more outcomes (or locations); and 3–phase-amplitude synchronization that detects seasonal behaviors of outcome-location pairs and examines whether the intensity of a seasonal peak varies in relation to its peak timing. We believe the synchronization of famine-related seasonal drivers is indicative of a complex dynamic because it generates non-linear, emergent crises. Instead of additive effects, synchronized stresses interact through feedback loops, creating rapid escalations that are far harder to predict and manage.

Second, famine evolution depends on the balance between competing forces that drive the progression toward famine and those that offer buffers and counterbalance [43]. We speculate that detection of seasonality in the basic and underlining drivers could be indicative of key features of a complex system in the context of crises, including competing forces and their balance, rapid escalations triggered by disturbances, and feedback loops that can either amplify or stabilize outcomes. Some factors could behave as stressors (or pressure forces) and drive the system away from equilibrium toward scarcity, malnutrition, and crisis; some can further escalate the conditions once certain thresholds are crossed, even without additional external shocks, Further investigations into seasonality synchronization might help us to contrast the self-reinforcing (positive) dynamics with self-correcting (negative) dynamics that can stabilize famine conditions.

Third, the ability to detect complex spatiotemporal alignments of conditions leading to famine help us with forming and testing hypotheses related to spatial dynamics sharing common seasonality features. Future research should focus on understanding the implications of seasonal synchonization and drivers of seasonal peaks in food insecurity and malnutrition.