  We report on the the long term monitoring campaign of the seemingly youngest
magnetar Swift~J1818.0-1607 at radio and X-ray wavelengths over a span of one
year. We obtained a coherent timing solution for the magnetar over the same
time span. The frequency derivative of the magnetar shows systematic variation
with the values oscillating about a mean value of $-$1.37$\times$10$^{-11}$ Hz
s$^{-1}$. The magnitude of the variation in the frequency derivative reduces
with time before converging on the mean value. We were able to identify four
states in the spin-frequency derivative that were quantified by the amount of
modulation about the mean value and the transition between these states seem to
be correlated with the change in the radio emission of the magnetar while no
correlation is seen in the average radio profile variability on a shorter
timescale (days). The 0.5--12 keV X-ray flux shows a monotonic decrease that
can be attributed to thermal emission from a hot-spot on the surface of the
neutron star that is reducing in size. Such decrease is consistent with what is
seen in other magnetars. The potential correlation between the radio emission
mode and the behaviour of the spin-down rate hints to a global change in the
magnetopshere of the magnetar akin to the correlation seen in a subset of
mode-changing radio pulsars and suggests a physical link between the two
sub-populations.
