HIV TESTING AND RISKY SEXUAL BEHAVIOUR: The ”nothing to lose” effect

People surprised by HIV-positive test results increase their risky sexual behaviour, exposing their partners to HIV infection and experiencing a more than nine-fold increase in sexually transmitted infections (STIs). That is the key finding of research by Erick Gong, published in the February 2015 issue of the Economic Journal.

HIV testing is encouraged in many sub-Saharan African countries battling AIDS epidemics. Millions of people are tested for HIV each year. Conventional wisdom is that those who learn they are HIV-positive will take steps to prevent infecting others. The new study shows that testing can have an adverse effect – specifically that those who unexpectedly learn they are HIV-positive have ''nothing to lose'' and increase their sexual activity.

The author recommends that anti-retrovirals (ARVs) be provided immediately to individuals who learn they are HIV-positive. Studies have found that ARVs can improve the health of those infected by HIV and dramatically reduce the likelihood that an HIV-positive individual infects his or her sexual partner. Immediately access to ARVs can thus counteract any adverse behavioural response to HIV-positive tests.

The study uses data from an experiment where over 1,900 individuals were enrolled in a randomised control trial in Kenya and Tanzania. A random half of individuals were offered HIV-testing, and over 90% agreed to be tested. Individuals surprised by HIV-positive test results subsequently increased their risky sexual behaviour – an unintended consequence of testing. There is good news however; those surprised by HIV-negative tests went on to decrease their risky sexual activity.

The study builds on a theory that HIV-testing shouldn''t affect someone unless the test result is unexpected. For example, someone who has been faithfully married for a long time probably believes that they are at low risk of HIV infection. If this person receives an HIV-negative test result, he or she should not dramatically change their behaviour; the HIV-test is providing information that the person already knew.

But if this same person receives an HIV-positive test, it would come as a surprise and this person would change their behaviour. An altruistic person would abstain from sex or use a condom consistently. A selfish person will believe there is ''nothing to lose'' and become more sexually active.

To see how people behave when they are surprised by their HIV-test, the study measures a person''s belief about their HIV-status before they are tested. When initial beliefs are at odds with the actual test result, a surprise is generated.

Sexual behaviour is very difficult to measure; it is typically unobserved activity and people may be reluctant to report truthfully their number of sexual partners or frequency of unprotected sex. Individuals enrolled in a study on HIV-testing might feel compelled to give researchers the ''correct'' answer and tell interviewers that they practice more safe sex after learning they are HIV-positive.

The new study surmounts this problem by using biological markers of unprotected sex, specifically gonorrhoea and chlamydia infections. STIs are contracted from unprotected sex and serve as a proxy for risky sex. The study shows that those surprised by HIV-positive tests have over a nine-fold increase in STIs.


''HIV Testing and Risky Sexual Behaviour'' by Erick Gong is published in the February 2015 issue of the Economic Journal. Erick Gong is at Middlebury College.


The experiment by the Voluntary HIV-1 Counselling and Testing Efficacy Study Group are summarised in ''Efficacy of Voluntary HIV-1 Counselling and Testing in Individuals and Couples in Kenya, Tanzania, and Trinidad: A Randomised Trial'', published in The Lancet Vol. 356: 103-12 (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2800%2902446-6/fulltext).