Complex sentence: Much of the research on symptoms of victimization is cross-sectional (researchers only collected data at one point in time), meaning the symptoms are associated with victimization; the causal relationship is not always being established in research, and alternative explanations have not been ruled out.
Split into simpler sentences: Much of the research on symptoms of victimization is cross-sectional (researchers only collected data at one point in time). From a research perspective this means that the symptoms are associated with victimization, but the causal relationship is not always established and alternative explanations have not been ruled out.