The more porn a man watches, the less sexually intimate he is with his female partner, a new study suggests.
The research, by a post-graduate student at Otago University in Christchurch, also shines a light on how frequently porn is used.
The study is based on information from 136 heterosexual women aged 18 to 78 on their own use of pornography, their attitudes to it, how frequently their partners use porn, and the degree of intimacy they experienced in their relationships.
Thirty-nine per cent of women said they had used pornography in the preceding 12 months and 65 per cent said their partner had used porn in that time.
For the 48 women who reported their partner had not used porn at all in the preceding 12 months, the mean sexual intimacy score was 65 - out of a maximum possible score of 96.
But for the 24 whose partners used porn at least weekly, the mean level of sexual intimacy was lower, at 55.
To measure sexual intimacy, the women ranked how strongly they agreed or disagreed with the statements:
• I am satisfied with the level of affection in our relationship,
• I am able to tell my partner when I want sexual intimacy,
• Sexual expression is an essential part of our relationship,
• I feel our level of affection is just routine,
• Because of my partner's lack of caring I hold back my sexual interest,
• My partner seems disinterested in sex.
The study also looked at emotional intimacy, social intimacy, intellectual intimacy and recreational intimacy.
The researcher, Anne Martin, a family therapist, found that women whose partners did not use pornography reported greater levels of emotional, sexual, intellectual and recreational intimacy.
Maori women experienced significantly more social intimacy in their relationships. As women aged, they experienced less sexual and emotional intimacy and tended towards more social intimacy.
Martin said porn is a growth industry but statistics for its use in New Zealand are limited.
"The study found many women have a positive attitude about pornography but for about 10 per cent of women pornography is a specific concern in their relationship."
Her research supervisor, clinical psychologist and addiction specialist Associate Professor Simon Adamson said the study could not separate cause and effect.
"It was not possible in this study to determine if pornography use reduced intimacy or if men in relationship with lower levels of intimacy in turn used pornography more.
"But there is certainly a clear enough picture here to indicate that this is something couples would benefit from talking about, either within their own relationships or in the context of couples therapy."
Frequency of porn use by men in the preceding 12 months (as reported by their partners):
35% - Not at all
32% - Monthly or less often
15% - 2 or 3 times a month
18% - At least weekly
61% - Not at all
29% - Monthly or less often
6% - 2 or 3 times a month
4% - At least weekly
78% - Not at all
18% - Monthly or less often
3% - 2 or 3 times a month
1% - At least weekly