When you think of clinical depression, you probably think of feeling sad and down for long periods of time; losing your energy and your interest in things you used to enjoy; sleeping too much or too little, or eating too much or too little. But besides these, depression can actually change your ability to think. It can impair your attention and memory, as well as your information processing and decision-making skills. It can also lower your cognitive flexibility (the ability to adapt your goals and strategies to changing situations) and executive functioning (the ability to take all the steps to get something done).
For people with severe depression, medications can provide some relief of low mood and energy, bolster the motivation to engage in enjoyable and important activities, and help people return to normal sleeping and eating patterns. (Notably, antidepressants are less helpful in general for mild and moderate depression.)
But we don’t know whether antidepressant medications treat cognitive impairment related to depression. Recently, an international research team attempted to answer this question as part of a larger study on depression treatment. Their results were published in The Lancet last month.
To study the effect of three common antidepressant medications on depression-related cognitive impairment, the researchers asked over 1,000 people with depression who were taking either escitalopram (Lexapro), sertraline (Zoloft), or venlafaxine-XR (Effexor-XR) to go through extensive cognitive testing. In short, none of the medications helped. Of these patients, 95% showed no improvement on any of the cognitive impairments mentioned above, and none of the three drugs was better than the others at improving cognitive symptoms.
This result is not completely surprising — antidepressant medications are mainly meant to help improve mood and increase the ability to participate in beneficial and enjoyable activities, two key aspects of depression treatment. It’s also worth noting that different parts and processes of the brain are responsible for cognitive (versus emotional) functioning; this may explain why the three drugs tested didn’t seem to help improve cognitive symptoms. New drugs for depression may be able to address these symptoms as well.
Beyond medications, problem-solving treatment can train people how to improve their problem-solving skills, and cognitive behavioral therapy can teach people to recognize and challenge distorted thinking patterns. Another approach, cognitive remediation therapy, uses practice drills to improve memory and executive functioning. Combining these behavioral interventions with antidepressants may yield better results for improving depression-related cognitive impairments.
There are some limitations to this study: it’s not known if the participants had cognitive impairments before they developed depression, and the length of drug treatment and follow-up was short — eight weeks in total. However, this study is important because the cognitive impairment symptoms of depression have received little attention — and haven’t necessarily been the target of medications for depression. It shows that we have a long way to go in helping people with depression return to a normal level of full mental functioning.