Adolescence can be hell; there's no doubt about it. The pressure of growing expectations, tides of hormones, and a brain that is melting down and reforming like a caterpillar in a neurological cocoon. It's little wonder that teenage years are hard.
For young women, such formative years appear to be even more emotionally challenging than for many young men, with studies showing an increase in generalized and social anxiety that isn't matched in adolescent males.
One contributing factor could be an "overactive braking system" interfering with thinking that would ordinarily rationalize through stressful situations.
A recent analysis conducted by psychologist Nicola Johnstone and cognitive neuroscientist Kathrin Cohen Kadosh from the University of Surrey in the UK has linked the rise and fall of two important metabolites in female brains with age.
Their study supports what's known as the neural over-inhibition hypothesis of anxiety, which proposes that disorders can emerge from an imbalance in the excitation and blocking of the brain circuitry that regulates emotional responses.
A significant amount of neurology depends on competition between chemicals that activate nerve cells and molecules that block their paths.
Glutamate and gamma-aminobutyric acid (GABA) are two examples of neurochemicals feuding over various switches inside some parts of our head, with glutamate demanding they stay on and GABA insisting they are turned off.
Knowing how each affects a behavior isn't as simple as knowing which one inhibits and which one excites. In some cases, turning off one circuit simply allows another to shine brighter.
For example, it's long been thought that higher levels of GABA in key regions of the brain keep a lid on anxiety. Yet recent investigations cast doubt on this claim, suggesting too much GABA in anatomical real estate devoted to higher-order functions like planning and decision-making might over-regulate, causing anxiety to emerge instead.
With this contrast in mind, Johnstone and Kadosh recruited 49 teen and pre-teen girls aged 10 to 12, and 32 young adult women aged 18 to 25. They surveyed each participant's history of mood disorders before analyzing their brain functions using an MRI scanner.
From the brain scans, they were able to estimate how GABA and glutamate ebb and flow in areas associated with reasoning and emotional processing, and correlate the differences with measures of anxiety among different age groups.
Though the study didn't focus on changes in activity or function delivered by the rise and fall of levels of GABA relative to glutamate, the researchers argue their measures – in context with previous research – support claims that anxiety bubbles out when neurochemistry dampens efforts to think out a problem, especially among the older volunteers.
"Our research indicates that the equilibrium between GABA and glutamate in the dorsolateral prefrontal cortex serves as a vital indicator of anxiety levels," says Johnstone.
"While glutamate propels brain activity, GABA acts as a brake. Our findings suggest that anxiety, often characterized by impaired rational thought, is intricately linked to the overactive braking system in the brain."
None of this is to say anxiety depends on sex, of course. Taken in context with other studies on male brains led by Cohen Kadosh, the circuits for stress generally differ between brains of different sexes, with male neurology coping with the extra GABA loads washing over the prefrontal cortex.
"Grasping how key brain chemicals, GABA and glutamate, fluctuate during important growth stages like adolescence is vital for spotting and stopping anxiety disorders early," says Cohen Kadosh.
"This study shines a light on the possibility of focusing on these brain chemicals for new treatments, particularly in young women."
This research was published in Developmental Cognitive Neuroscience.