Effects of behavioural activation with and without citalopram on emotional cognition and mood

A body of research literature has shown that patients with depression tend to have a bias towards negative stimuli in their automatic cognitive processes. For example, depression is linked to a relative increase in attention to and memory for negative words and facial expressions (Roiser & Sahakian, 2013) as well as a decrease in the positive bias for ambiguous stimuli that is found in healthy samples (Milders et al., 2010). Rather than just being an epiphenomenon, evidence suggests that these biases might play a causal role by being a risk factor for depression onset (Joormann, Talbot, & Gotlib, 2007) as well as a possible predictor of relapse (Bouhuys, Geerts & Gordijn, 1999).

Importantly, positive changes in these automatic biases have been linked to the early phase of antidepressant drug treatment (Harmer et al., 2003). Harmer, Goodwin and Cowen (2009) have proposed a cognitive neuropsychological model of antidepressant drug mechanism whereby early changes in automatic processing of emotional stimuli occur before conscious changes in mood. In line with this, Tranter et al. (2009) found evidence that early changes in the automatic bias for facial expression recognition at two weeks of drug treatment may be predictive of treatment success at six weeks. However, it is not clear why this early change in affective bias does not occur for everyone and many people don't respond to their first line antidepressant treatment.

As suggested by Harmer et al. (2017), the early cognitive changes in affective bias induced by drug treatment are expected to interact with positive environmental reinforcement to eventually improve mood. If positive environmental reinforcement is necessary for interacting with the drug-induced positive bias and thus potentiating drug efficacy, this could explain variability in how patients respond to antidepressant drugs. Indeed, several lines of evidence suggest the importance of environmental reinforcement in antidepressant treatment. For instance, Shiroma et al. (2014) found that increase in positive bias after antidepressant administration was greater in patients with higher levels of social support. This is also consistent with evidence from animal research wherein animals in better environments show a better response to antidepressant drugs, as well as higher brain BDNF levels (Branchi et al., 2006).

To our knowledge, the interaction between antidepressant effects and environmental reinforcement has not been experimentally tested in humans. The aim of this DPhil is to examine the role of environmental reinforcement on cognitive biases with and without added antidepressant treatment, using behavioural activation (BA). This is a NICE-recommended depression treatment (National Institute of Health and Care Excellence, [NICE], 2009), which aims to increase patients' activity and environmental reward by helping them get back to abandoned activities before they feel motivated for it. This is achieved through a structured programme of activity monitoring, gradual goal setting and coach-like support.

The purpose of the first study is to test the early effects of a BA intervention on emotional cognition and mood. We aim to recruit 90 participants and randomise them into either 1) 4 weeks of BA, 2) 4 weeks of activity monitoring (active control group) or 3) passive control group, while collecting data at the beginning, middle and end of the intervention. The second experiment of this DPhil will combine BA with antidepressant drug treatment for 2 weeks to examine the early effects on cognitive biases. We aim to recruit 120 participants experiencing depression and randomise them into four groups (BA with antidepressants, BA with placebo, antidepressants alone and placebo alone). Overall, this should aid our understanding of the onset of early cognitive changes in different depression treatment types.