The phrase "a more negative influence" is correct and usable in written English.
It can be used when comparing the impact of different factors or entities, indicating that one has a greater negative effect than another.
Example: "The new policy has had a more negative influence on employee morale than we initially anticipated."
Alternatives: "a greater adverse effect" or "a stronger detrimental impact".
While last week saw adult entertainer Ron Jeremy claiming games were a more negative influence than porn, this week's naysayer is the president of Venezuela, Hugo Chavez.
However, whether nocturia or sleep disturbance has a more negative influence on the quality of life (QOL) of individuals remains unclear.
While the frequency of tests might not affect student well-being, there does seem to be a more negative influence if tests are seen as "threatening".
In fact, research indicates that a bad mentoring experience has a more negative influence on mentees' wellbeing than a good mentoring experience has a positive influence; negative relationships are, in a word, stronger.
In addition, smoking and inflammation (detected by a high CRP level) have been reported to have a more negative influence on coronary artery disease in women than in men.
Moreover, a systematic review investigating the quality of life in infertile couples, found evidence of more negative influence of infertility in infertile women than in infertile men (Chachamovich et al., 2010).
It was well positioned, she said, to "neutralise somewhat the more negative influence on Pakistan politics and society exercised by Saudi Arabia".
Results reveal that divalent cations may exert more negative influence on boron rejection owing to the competition between them and boron to form complexes with chelating polymers.
Hill balances the ideals of the period with some of the more negative influences, but mostly he celebrates the rise of consciousness-raising movements and their impact on future generations.
Even though we are hardwired for kindness and empathy, we can be hampered by the busyness in our lives or by more negative influences in the world, like bullying, intolerance, hate crimes, and more.
While Internet addicts perceived the Internet to have significantly more negative influences on daily routines, school performance, teacher and parental relation than non-addicts, both Internet addicts and non-addicts viewed Internet use as enhancing peer relations.
