Existent research is plagued with methodological limitations including inattention to selection effects and reliance on mostly cross-sectional designs.
The reviewed studies were from different parts of the world, confirming the worldwide application, and mostly cross-sectional.
Up to the present, mostly cross-sectional studies have explored such an association without providing a clear temporal relationship between social capital and depression.
The advantages come at the price of concerns about the limited number of country observations, the mostly cross-sectional character of available achievement data, and possible bias from unobserved country factors such as culture.
Of the 430 references identified, 47 (mostly cross-sectional and ecological designs) referred to arsenic concentration in water and its relationship with the incidence and mortality of cancer, dermatological diseases and genetic disorders.
Generally, the results of this longitudinal study replicate two aspects of previous, mostly cross-sectional findings, using US and European data.
Studies comparing muscle testing scores in DMD patients are mostly cross-sectional [11] [13].
The design of the selected studies was mostly cross-sectional, except for two studies which employed case control design.
Causality, and the potential bidirectional nature thereof, cannot yet be definitively determined from available, mostly cross-sectional evidence.
