Final answer:
Since 2000, research into the biological basis of anxiety and depression has employed techniques like fMRI and PET, examined neurotransmitters like serotonin, and explored genetic epidemiology and the effects of stress to understand these mental health conditions better.
Step-by-step explanation:
Since 2000, a variety of methods have been used to investigate the biological basis of anxiety, depression, and related disorders. Neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans have allowed researchers to observe brain structures and functions in real-time. Studies exploring the role of neurotransmitters have also been crucial, particularly concerning the influence of serotonin and norepinephrine on mood disorders.
Genetic epidemiology has shed light on the heritability and genetic risk factors for anxiety disorders. Additionally, the interplay between neurobiological changes and environmental stressors has been examined to understand how chronic stress may lead to depression. Together, these approaches have significantly expanded our understanding of the neurobiological underpinnings of anxiety and depression.