Why do antidepressants take so long to kick in?

There are many different methods and treatment combinations to improve the conditions of those experiencing mental health issues. Eating better, exercising more, avoiding social media, attending regular therapy or counseling sessions and even taking ketamine or other experimental drugs are all options depending on individual accessibility. For those going the basic pharmaceutical route, though, antidepressants are a popular way to go. 

Some scientists think antidepressants – from commonly prescribed SSRIs to SNRIs to NDRIs – don’t work well at all and that they’re more or less a placebo. But, they’re efficacy is backed by many others.

If you’ve ever taken antidepressants, though, you know that they can take ages to actually kick in – for the benefits of these meds to be felt. Why is that?

“The best clinical trials and meta-analyses, most of them indicate that there’s some medication effect,” says Dr. David Hellerstein, a clinical psychiatry professor at Columbia University. “I would say it’s less than we would like it to be.” 

Based on personal brain chemistry, everyone reacts to specific medications in different ways, sometimes not responding, period. Still, these meds can take as many as eight weeks to improve depression and anxiety symptoms for some, if they end up experiencing benefits at all. 

Let’s talk selective serotonin reuptake inhibitors, or SSRIs – by far the most popular antidepressant meds out there (think Prozac and Zoloft). These drugs alter the way that neurons take in serotonin, allowing more of that chemical into the brain. This is usually the first type of antidepressant prescribed to a patient. There are a few different proposed theories as to why these could take a while to work.

But the results of a new study presented at the ECNP conference in Barcelona on October 9 suggest that taking SSRIs allows for new neuron connections, or synapses, to be generated, especially in brain regions associated with depression and anxiety. Scientists propose that antidepressants take a while to really work because it takes time for synapses to grow and mature.

This is one of the first pieces of evidence that these drugs do take time to work, and they do work through increasing the number of synaptic contacts between nerve cells,” says Gitte Knudsen, a neurobiologist and neurologist at the University of Copenhagen, Denmark, who led the study.