Many factors can lead to a sexless or low-sex marriage. If there’s a “desire discrepancy”, as California-based sex therapist Christene Lozano puts it, that imbalance can grow over time if the couple doesn’t do a good job of addressing it. The person who wants more sex and keeps initiating it might give up and lose self-esteem if they continue to get rejected, for instance. Meanwhile, the partner doing the rejecting might feel increasingly guilty, altogether creating even worse conditions for fostering arousal.