In this module, you’ll learn about key body systems influencing the brain and how to analyze and treat these systems effectively using advanced interview, screening, laboratory, and diagnostic techniques. These systems can be organized by the acronym "HPAGGTIE" and include the hypothalamic-pituitary-adrenal axis, the hypothalamic-pituitary-gonadal axis, the gut-brain axis (including detoxification), the hypothalamic-pituitary-thyroid axis (and metabolism), the immune-brain axis, and epigenetics.

What occurs above the neck reflects what occurs below the neck. The brain and the body are inextricably linked in a dynamic dance. I like to refer to the interrelated nature of systems as the bodymind. The siloing of care in Western medicine has led us to focus on organ systems outside their contexts. Therefore the mind and body, just as the brainmind, are not separate but interrelated aspects of an individual. The following sections will examine how several systems loosely relate to neurological functioning.

While clarifying what the individual experiences, look for clues suggesting specific body system abnormalities. An effective initial strategy is to focus on the individual’s body sensations when emotional experiences are heightened. For example, if an individual experiences abdominal discomfort when anxious, it may be effective to analyze the gut in more detail. If an individual experiences rashes upon provocation, it may be worthwhile to explore the immune-brain axis. If the individual experiences a perimenstrual correlation with symptoms, then examining hormones may prove useful. Aside from following sensations and patterns, the clinician will likely benefit from reviewing systems to explore key systems. In many cases, it will be beneficial to evaluate baseline laboratory and diagnostic studies given that there are some bodily-based abnormalities that have a more generalized influence on a variety of psychiatric symptoms.

The main systems that make up the dynamic dance include the adrenal, gonadal, gastrointestinal, metabolic, thyroid, and immune systems. These systems impact each other in various ways and have been interdependently implicated in neuropsychiatric functioning. Examination of these systems illuminates several root causes of psychiatric illness, and, when optimized, this dance occurs much more fluidly and can be appreciated in the form of mental health and well-being.