Background and aim Conflicting or insignificant results of studies into the effect of promising nursing interventions are not uncommon. Recently, we conducted a study into the effect on NICU-related parental stress of a new nurse-parent communication intervention. Surprisingly, we were not able to show the effect of the intervention in a randomised controlled trial although we found that parents experienced the intervention as supportive compared to standard care. The aim of this presentation is to present the conflicting evidence of the effect and significance of the Guided Family-Centred Care (GFCC); discuss possible reasons why we may have been unable to show effect; and discuss potential ways for handling such matters.

Methods Evaluation of the results of the GFCC study within the framework of current literature on challenges of evaluating complex interventions.

Results Lack of effect may not necessarily reflect ineffectiveness of an intervention. In our study, there may be a number of possible explanations for being unable to show effect, such as spill over between the groups, or a too modest “dose” of the intervention. Another explanation might be that the outcome measures were not sensitive to the intervention effect. Results from the interview study indicated that other outcome measures such as parent strength and empowerment might have been relevant. However, such instruments are lacking.

Conclusion It may be necessary to develop new instruments sensitive to human interaction to demonstrate effect of nursing interventions. Furthermore, incorporating multiple methods, sources and perspectives are needed when evaluating effect of complex interventions.