  - Aims: We intended to quantify the impact of stellar multiplicity on the
presence and properties of exoplanets. - Methods: We investigated all exoplanet
host stars at less than 100 pc using the latest astrometric data from Gaia DR3
and advanced statistical methodologies. We complemented our search for common
proper motion and parallax companions with data from the Washington Double Star
catalogue and the literature. After excluding a number of systems based on
radial velocity data, and membership in clusters and open associations, or with
resolved ultracool companions, we kept 215 exoplanet host stars in 212
multiple-star systems. - Results: We found 17 new companions in the systems of
15 known exoplanet host stars, measured precise angular and projected physical
separations and position angles for 236 pairs of stars, compiled key parameters
for 276 planets in multiple systems, and established a comparison sample
comprising 687 single stars with exoplanets. With all of this, we statistically
analysed a series of hypothesis regarding planets in multiple stellar systems.
Although they are only statistically significant at a 2{\sigma} level, our
analysis pointed to several interesting results on the comparison in the mean
number of planets in multiple versus single stellar systems and the tendency of
high mass planets to be located in closer orbits in multiple systems. We
confirm that planets in multiple systems tend to have orbits with larger
eccentricities than those in single systems. In particular, we found a
significant (> 4{\sigma}) preference for planets to exhibit high orbital
eccentricities at small ratios between star-star projected physical separations
and star-planet semi-major axes.
