  We discuss whether the bound nature of multiquark states in quark models
could benefit from relativistic effects on the kinetic energy operator. For
mesons and baryons, relativistic corrections to the kinetic energy lead to
lower energies, and thus call for a retuning of the parameters of the model.
For multiquark states, as well as their respective thresholds, a comparison is
made of the results obtained with non-relativistic and relativistic kinetic
energy. It is found that the binding energy is lower in the relativistic case.
In particular, $QQ\bar q\bar q$ tetraquarks with double heavy flavor become
stable for a larger ratio of the heavy to light quark masses; and the all-heavy
tetraquarks $QQ\bar Q\bar Q$ that are not stable in standard non-relativistic
quark models remain unstable when a relativistic form of kinetic energy is
adopted
