Sentence:  The pain and distress <WSD>associated</WSD> with the performance may easily give the wife a deep-seated dread of marital relations and cause her , unconsciously , to make the sex act unpleasant and difficult for both by exercising her vaginal muscles to complicate his penetration instead of relaxing them to facilitate it . 
Meaning of the word marked with <WSD> tags:  make a logical or causal connection