Assertion: schizophrenia's relationship | /r/HasProperty | difficult to establish
Facets:
value: often
type: TEMPORAL
Source sentences:
text: Most research on predictive factors is correlational in nature, however, and a clear cause-and-effect relationship is often difficult to establish.
text: Most studies done on this subject, however, are correlational in nature, and a clear cause-and-effect relationship is difficult to establish.