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The Biology of Borderline Personality Disorder and Bipolar Disorder

Updated: Dec 13, 2022

Sepia tones drawing of the brain, hemisphere
Sketch of Brain

The DSM classifies Borderline Personality Disorder, Schizophrenia, Bipolar Disorder as mental illnesses with specific criteria for all three. Medication is recommended in addition to counseling to manage these 3 types of mental illness.

1. Puberty and Schizophrenia, Borderline Personality Disorder and Bipolar
illustration of caricature emoticons.

All three diseases manifest during puberty, unlike ADHD, Autism, OCD, and Learning Disorders. It is hypothesized that all three Schizophrenia, BPD, BP are associated with disorganized pons pruning that occurs during puberty. MRIs and autopsies support this theory. The brain structures of people living with these disorders differ from typical brain structures. All three disorders are biological in nature and persistent throughout the individual’s lifespan. It is unlikely that these psychotic disorders can be successfully treated with counseling alone and medication is required to manage symptoms. During puberty, the brain enters the second stage of pons pruning. Pons act as the bridge between the cerebrum (the two hemispheres of the brain above the corpus callosum) and cerebellum (the deep brain below the corpus callosum). (2021, Pruning of the pons coincides with the development of Autism, Learning Disorders, ADHD, and likely signals atypical brain structures. A biological symptom of autism is uneven development of the corpus callosum (Grandin, T., The autistic brain, 2013).

2. Puberty and Hormones

Intense fight between two male Gemsbok (type of antelope) on dusty plains of Etosha
Intense Hormones

During puberty, hormones increase and pruning re-occurs. Pubescent children experience mood swings, impulsive actions, and thought dysregulation during this period of life driven by hormonal changes that prepare the body for reproduction. Signals from the lower brain are disrupted as they pass through the corpus callosum to the upper brain, where speech, actions, and logic are formed, and back again. Hormone activity can confuse this process. Your child may really not understand why they are did what they did. Actions and thoughts can be as confounding for the child as the parent.

3. Corpus Callosum and Organization
3D illustration male nervous system, medical concept.
Male nervous system

The corpus callosum functions similarly to the primordial streak, the first thing an embryo makes. The primordial streak separates embryonic cells sending either to the left or right. In most mammals the result is the right side mirrors the left side, more or less.

The corpus callosum sorts neurological signals and sends them to the correct area of the brain. If the pruning process is erratic then the messages get confusing too. The anatomical disparity, irregularities to the corpus callosum results in unpredictable development/behaviour. These behaviours are typical to a person whose brain is wired differently.

3. Diverse Functions

Synapse and neuron on a blue background. 3d rendering.
Synapse and neuron

Further complicating this disruption are structural changes to where and how signals are processed. A chatty child or auditory hallucinations may actually indicate an irregular flow of lower brain signals to the verbal/left hemisphere. Uncoordinated movement can be the result of sudden physical growth combined with confusing looping signals from the lower brain to the non-verbal/right hemisphere (Gazzaniga, M, Tales from both sides of the brain, 2016). This theory is often supported by parents and teachers of children with learning and language processing disabilities. Pons send signals from the deep brain to the corpus callosum and affect the corpus callosum’s development. Pons pruning is a natural process that occurs at two major junctures in human development, the period when the child leaves infancy to childhood, and when the child is in puberty. The period of puberty continues until the individual’s hormonal levels, primarily testosterone and progesterone are relatively stable. During that adjustment period estrogen, which is converted to produce sex hormones, fluctuates radically. A German study discovered males with BP and

had periods of estrogen depletion associated with suicidality. There is an unknown association between pons pruning and estrogen.

4. Living successfully with neurodiversity
Calm brain meditating cartoon
Zen Brain

Counseling is helpful in learning to manage the symptoms of BPD and BP, but is ineffective in reducing the actual disease, as both are organic in nature. Cancer patients receiving counseling live longer often with a better quality of life but their disease persists. The disease requires medical intervention for effective treatment, but the quality of life and survival rates can increase with counseling to manage symptoms and adjust to the effects of living with a chronic illness. Unfortunately, medical research into BPD and BP is lagging and medication development has not changed since the 1950s. As more is learned about brain development it is hoped that more effective, targeted therapies will be developed. For parents and siblings of people living with BPD and BP, it is important to understand that both diseases have high fatality rates and are organic in nature but with supportive environmental changes and counseling, it is possible to improve quality of life and longevity for their loved ones.


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