Background: Despite the known associations between anxiety, depression and suicide ideation, we know little of the course of these constructs over time.There is some evidence that declines in depressive symptoms predict declines in suicide ideation in adults with major depression, but the evidence is less clear in adolescence.Anxiety is increasingly recognised as a risk factor for suicide ideation and suicide attempt, but the temporal relationship among the measures has rarely been examined.One method to determine the short term relationship, and, indeed, gain some knowledge of the causal links among these constructs, is to examine the effects of treatment on these symptoms over time.Very few studies have mapped the time course of suicide ideation through the course of an antidepressant RCT (Mann, 2005) or in response to psychological therapy.In an earlier trial of callers to a telephone counselling service (Farrer et al., submitted) an Internet based CBT program reduced depression symptoms relative to a control condition, but that both the Internet program and the control condition were equally effective in reducing suicide ideation over 6-weeks.The present study investigated the effects of an Internet CBT program on anxiety and suicide ideation in a new RCT trial which aimed to prevent the development of Generalised Anxiety Disorder.We hypothesized that the CBT program would lower anxiety, but that both the control and the CBT intervention arms would lower suicide ideation.Methods: The study consisted of 5 arms: GAD-Internet prevention alone, GAD-Internet with human interaction (telephone), GAD Internet with automated email messages, a placebo Internet intervention plus human interaction (telephone), and the placebo Internet (alone).Participants were recruited from a community sample of 18-30 year-olds with subclinical GAD symptoms.Results: Preliminary data indicated that the GAD internet intervention substantially reduced levels of anxiety compared to the placebo internet conditions.However, the intervention did not significantly decrease suicide ideation.A preliminary analysis of completers using logistic regression (n=82 of 127) examined suicide ideation at post-test as a function of changes in depression and anxiety.Accounting for pre-test GAD-7 scores, group assignment and pre-test suicidality, increases (or smaller decreases) in GAD-7 scores from pre-to post-test was significantly associated with higher odds of suicidality at post-test.Initial depression, depression change scores, age and gender did not predict suicidality after accounting for anxiety.Discussion: An internet based GAD program significantly reduced levels of anxiety.Although the program did not significantly reduce levels of suicide ideation, participants with larger reductions in anxiety were less likely to experience ideation at post-test.Changes in depression did not predict changes in suicide ideation.These results may be specific to individuals at risk of GAD.Methodological limitations include low numbers, short time frame (pre to post), completer analysis, and low levels of suicide ideation at pre-test.Anxiety and ideation may be more strongly linked than depression and suicide ideation.Findings for the larger sample of 300 participants will be presented in September.