Is luvox (fluvoxamine) the only ssri that is a sigma agonist...And is that why it is better for anxiety. Explain sigma a sigma agonist?

See Wikipedia . Drugs known to be ?–agonists include cocaine, morphine/diacetylmorphine, opipramol, pcp, fluvoxamine, methamphetamine, dextromethorphan, and the herbal antidepressant berberine. However the exact role of ?–receptors is difficult to establish as many ?–agonists also bind to other targets such as the ?-opioid receptor and the nmda receptor.Recently selective ?–receptor agonists were shown to produceantidepressant effects in mice. Best wishes.
Luvox. Fluvoxamine is FDA approved for the treatment of Obsessive Compulsive disorder. It would have to be used off-label for anxiety disorders. A sigma receptor is a non-opiod receptor that binds to different drugs. Here is an excellent abstract: