If you look at the abstract, all of the correlations actually show that having a cat does predict mental illness at all ages considered. But the effect sizes are relatively low (albeit consistent with the more direct studies looking at people actually infected with toxoplasma rather than people who might be infected), so with a few hundred or thousand people, it technically doesn't satisfy p<0.05. Nevertheless, this is further evidence for toxoplasma having bad effects.

This seems to be a trend with toxo papers - take a too-small sample, do no power or Bayesian analysis, find all bad correlations, but declare evidence of safety anyway.