The new evidence that explains what anxiety really is

WHEN I was asked to write this article, my heart started beating faster, my hands started shaking and my thoughts went into overdrive coming up with what felt like hundreds of objectively sensible reasons why I couldn’t do it. I could tell you that as chief subeditor at New Scientist I don’t often get a chance to write. But the truth is I rarely write because I am very anxious about it. What if the people I contact don’t respond? What if I write something stupid? What if I am stupid? What if, what if, what if.

Clearly, I chose to write this article, partly because I am stubborn and hate that these anxious feelings hold me back from doing things I might enjoy, and partly because I find that doing the things that make me anxious helps me overcome that feeling (see “Five scientific ways to help reduce feelings of anxiety”). But my main motivation was to answer questions that have been bothering me for years: what exactly is anxiety and what is happening in my body and brain to cause this feeling?

Answering that first question is difficult, in part because there is no one way to feel anxious. “I’d say there’s as many types of anxiety as there are people in the world,” says Oliver Robinson, head of the Anxiety Lab at University College London.

We do know everyone experiences anxiety – it helps prime us to be ready in possibly risky situations. Consider walking home alone in the dark, where that feeling of being on edge and alert may help you to react if the unexpected happens. Where it becomes more of a problem is if you still feel like that when you are safe at home. “Anxiety is a threat response in the absence of a threat-inducing stimulus,” says Sahib Khalsa at the Laureate Institute for Brain Research in Tulsa, Oklahoma.

We don’t know exactly what is happening in the brain when you are anxious, says Robinson. However, one area that has had a lot of attention is the amygdala, as it deals with fear-related memories and is involved in detecting danger and helping conjure involuntary emotional responses.

When it has picked up a potential external threat, the amygdala sends signals to the prefrontal cortex, the region at the front of the brain that deals with complex functions like emotional regulation. Then, two sections of this region step in: either the dorsomedial prefrontal cortex tells the amygdala to pay attention to these signals or the ventromedial prefrontal cortex dampens them. We think that, in an anxiety disorder, this normally helpful process goes awry, so that you experience anxiety at inappropriate times or too intensely, says Robinson (See “Anxiety vs anxiety disorders”, below).

But potential threats that spark anxiety don’t only come from external sources. “There could be a change within your body and you then have a threat perception,” says Khalsa. This is due to something called interoception. Often referred to as our sixth sense, interoception is how our brain keeps tabs on what is happening within the body, subconsciously monitoring things like muscle tension and carbon dioxide levels in the blood. “Oftentimes, anxiety is a misinterpretation of a [physiological] signal,” says Khalsa. Becoming aware of a change in heart rate, for example, could induce anxiety by making you think you are having a heart attack.

Evidence that higher interoceptive awareness may contribute to feelings of anxiety came when 24 women with generalised anxiety disorder (GAD) were given 0.5 micrograms of the drug isoproterenol to increase their heart rates. They experienced larger changes in the response of their brains to heartbeat, thought to be a measure of cardiac interoception, than 24 controls without the condition. Prior to taking isoproterenol, the women with GAD also had a higher measure of cardiac interoception than the control group.

Given anxiety seems to depend on this connection between mind and body, where does the initial trigger start, in the brain or in the body? “We don’t know,” says Khalsa. “Some would say that the two are happening simultaneously. It is close enough in time that, for all intents and purposes, it doesn’t matter.” What seems clear is that both parts play a role in anxiety. “If you think about it in evolutionary terms, having this feedback loop is probably useful, because it means that you’re able to adapt and update your perceptions,” he says.

So, did learning about what happens when I feel anxious help when writing this article? A little. I have no plans to switch careers, but the next time I am asked to write about something I am interested in, I plan to take control of my overactive anxiety response and say yes without hesitating.