The best ways to investigate this sort of claim do include looking in decent dictionaries.

Compare the first-given (and in a non-historical dictionary, this indicates frequency of this sense being the intended one) definitions for the transitive usage/s at [AHDEL, Collins and RHK Webster's](http://www.thefreedictionary.com/affect):

> 1. To have an influence on or effect a change in: Inflation affects the buying power of the dollar.  [AHDEL]
> 
> 1. to act upon or influence, esp in an adverse way: damp affected the sparking plugs.
> 
> 1. to produce an effect or change in: Cold weather affected the crops.

So there is at least a connotation of a negative (in the sense of adverse) effect.

This is doubtless compounded by the most usual sense of the homonym:

affect[2] 1. To put on a false show of; simulate [AHDEL]

This is not to say that these vibes will be picked up identically by all people, and certainly not in all contests (The mass of a planet will obviously affect its gravity).