"questionable effect" is correct and usable in written English.
You can use it when you want to indicate an effect or outcome that is questionable in terms of its validity or correctness. For example, you could say, "The new policy had a questionable effect on the company's stock prices."
As obesity has become a health concern globally, weight loss information has proliferated throughout the country - with questionable effect on the prevalence of obesity.
From this study supplemental iron would appear to have had a questionable effect in the immediate aftermath of malaria when erythropoetic iron need can only have been met by the release of sequestrated iron.
Greater effort should be taken in the early detection and complete resection of TP53-associated malignancies, since DNA-damaging, standard adjuvant therapies not only have a questionable effect, but also carry the risk for secondary tumours.
Beacause of many drawbacks and questionable effects of conventional palatal expander that are either tooth-borne or tooth-and-tissue-borne, the bone-borne maxillary distractors have been developed to deliver the expansion force directly to the basal bone and to overcome the dental complications.
For example, it has only been through longer term surveillance following the swine flu scare of 2009/2010 that the questionable effects of the "swine flu jab" (Pandemrix) have come to light (CDC 2010).
It is questionable whether effect sizes of 20% or smaller are reliable predictors of harmless effects on a range of non-target organisms in the field, when testing the GMO at lower tier, e.g. in the laboratory.
In tension type headache, a questionable specific effect is also reported for acupuncture and for BFB associated with relaxation, and, by one study for relaxation.
This makes questionable the effect of fructose per se for increasing food intake, inducing weight gain and metabolic diseases [ 16].
However, it is questionable which effect morcellation has on the progress of the disease or which progress would have been observed after abdominal hysterectomy or no operation in case of an enlarged uterus weighting over 1000 g.
Size helps the Met make a living, even if the questionable artistic effects of its 3,800 seats are magnified on evenings like this one.
It can also have questionable economic effects, increasing the number of local people who serve tourists at hotels and restaurants and such.
