Europe's most homophobic countries may be paving the way for a rise in HIV cases among gay and bisexual men, according to new research published in the journal AIDS.

An international team of researchers from Europe and the US looked at HIV-related service use, need and behaviours among 175,000 gay or bisexual men living in 38 European countries with differing levels of national homophobia.

They found that men in homophobic countries had fewer sexual partners and were less likely to be diagnosed with HIV. However, they also found those men knew less about HIV, were less likely to use condoms and are at greater potential risk of getting HIV when they do have sex.

As technological advancements such as mobile sex-seeking apps mean men in the most homophobic countries have increasing opportunities for sexual contact, they are quickly overcoming the relative lack of brick-and-mortar sex venues such as bars and saunas. The researchers warn the effects of homophobia could therefore have a very concerning impact on the spread of HIV.

Co-author Dr Ford Hickson from the London School of Hygiene&Tropical Medicine, said: "Our findings are surprising as it may appear it's effectively safer for men to stay in the closet in the most homophobic countries because their HIV-risk is lower there. But the closet is a difficult, shameful place which is particularly harmful to mental health and wellbeing. It's also a place where men are kept ignorant, under-resourced and poorly skilled when dealing with sex and HIV. As the way people meet changes with technology, the homophobia that may have appeared to be protecting these men will now be exposing them to huge risk."

The research was conducted by the Yale School of Public Health, Columbia University, the London School of Hygiene & Tropical Medicine, the Norwegian Knowledge Centre for Health Services, and the German Robert Koch Institute.

Researchers measured national homophobia across Europe using a combination of the laws of a country and the results of social attitudes surveys. They then analysed data from 175,000 gay or bisexual men in 38 European countries who completed the European MSM Survey (EMIS) in 2010 to compare the level of HIV-related service use, need and behaviours among groups of men living in more homophobic and less homophobic countries.

The researchers say their findings suggest new approaches need to be considered to reduce oppression without increasing the HIV risk.

Dr Hickson added: "Previous research on HIV prevention in Europe has shown there are four key interventions in suppressing HIV: condom distribution, peer-led group education, peer-outreach education projects, and universal access to anti-retrovirals for men with HIV. All health authorities could be commissioning these services as well as working to protect the human rights of sexual minorities."

Citation: J E Pachankis, M L Hatzenbuehler, F Hickson, P Weatherburn, R Berg, U Marcus, U, A J Schmidt. Hidden from health: Structural stigma, sexual orientation concealment, and HIV across 38 countries in the European MSM Internet Survey (EMIS). AIDS. DOI:10.1097/QAD.0000000000000724