The Five Stages of Brain Development

Scott LaFee
Tue, 27 Jan 2026 21:00:00 -0800
Lifestyle

Researchers now suggest that the human brain goes through five distinct phases of development over the course of a lifetime.

1. Childhood, from birth to age 9, during which time the brain is continually pruning away haphazardly created synaptic connections forged as early learning, unlearning and relearning chaotically occurs. As a result, while it is a time of rapid growth, it is not a time of great efficiency.

2. Adolescence, from age 9 until about age 32, is the most efficient phase. It's a time when new synaptic connections are most easily formed. Mental disorders are also most likely to begin during the adolescence epoch.
Updated: Wed Jan 28, 2026

Researchers now suggest that the human brain goes through five distinct phases of development over the course of a lifetime.

1. Childhood, from birth to age 9, during which time the brain is continually pruning away haphazardly created synaptic connections forged as early learning, unlearning and relearning chaotically occurs. As a result, while it is a time of rapid growth, it is not a time of great efficiency.

2. Adolescence, from age 9 until about age 32, is the most efficient phase. It's a time when new synaptic connections are most easily formed. Mental disorders are also most likely to begin during the adolescence epoch.

3. Adulthood, from age 32 to age 66, is the longest of the epochs. In adulthood, brain efficiency slows way down. At the same time, this is typically a period of maximum stability.

4. Early aging, from 66 to 83 years of age, during which time brain patterns begin to shift, with some regions interoperating more tightly together while others begin to operate less cohesively. It's when dementia and systemic issues like cardiovascular problems are more likely to begin appearing.

5. Late aging, from 83 and beyond. This period is similar to early aging, but changes are likely to occur at an accelerated pace.

Body of Knowledge

The human body has many, many sphincter muscles — at least 60. They range in size from microscopic to the paired internal and external anal sphincters, which are approximately 1-2 inches long and 1-3 inches thick. By definition, sphincter muscles are responsible for controlling the body's many openings, from those in the digestive and urinary tracts to the pupils of the eyes and in the capillaries of the cardiovascular system.

Counts

7: Billions of dollars that Sackler family members have agreed to pay over 15 years to settle thousands of lawsuits over the harms of opioids. The Sacklers owned Purdue Pharma, which became notorious for promoting the use of OxyContin, a commonly abused opioid. The company went bankrupt in 2019 and restructured as Knoa Pharma (Source: STAT News).

Stories for the Waiting Room

In a first-of-its-kind randomized trial, people who smoked weed consumed less alcohol in the two hours afterward than those who did not. Nonetheless, researchers cautioned against interpreting the findings as favoring any particular lifestyle choice.

Doc Talk

Fasciculation: A superficial muscle twitch, visible beneath the skin

Mania of the Week

Dermatillomania: Excessive picking at one's skin

Onychotillomania: When that obsession focuses on fingernails

Best Medicine

First woman: "Did you hear that health experts say 25% of all men are on some form of medication for mental illness?"

Second woman: "That's horrible!"

First woman: "Yes, that means 75% are going around untreated."

Hypochondriac's Guide

Trombone player's lung is a colloquial term for hypersensitive pneumonitis, a general medical term for inflammation of the lungs caused by inhaling bacteria-laden dust, vapor or, in this case, the microbe-rich air from inside a brass instrument. It's not a unique affliction. Variations of it are sauna worker's lung, bird fancier's lung, cheese-washer's lung and snuff-taker's lung.

Trombone players face an additional risk: horn player's palsy. This is a form of facial paralysis caused by the nerves of the face being damaged by the high air pressures required to play instruments like the trombone or trumpet.

Observation

Did you hear about the guy who was arrested after his therapist suggested he take something for his kleptomania?

Medical History

This week in 1998, a new glue called Dermabond debuted as a replacement for painful stitches. The manufacturer, Closure Medical, said Dermabond could seal off certain wounds quickly without the need for painful shots. A doctor simply pressed the cut's edges together and painted the glue across the top. Proper medical application required skill and practice, so the glue isn't meant for home use. Dermabond was the chemical cousin of Krazy Glue, which is too toxic to repair wounds.

Self-Exam

Correctly match these numbers with the human body component.

1. 630

2. 78 (give or take)

3. 50,000

4. 3 million

A) Distinguishable odors

B) Sweat glands

C) Organs

D) Joints

Answers: 1-D; 2-C: 3-A; 4-B

Med School

Q: What moves food down the trachea?

A) Peristalsis

B) Motility

C) Segmentation

D) Constipation

A: A) Peristalsis is the involuntary movement of longitudinal and circular muscles, primarily in the digestive tract, that create progressive wavelike contractions. Extra credit if you noted that food moves down the esophagus, not the trachea (more commonly known as the windpipe). Food in the trachea is not good, often leading to what's commonly called choking or worse, asphyxiation.

Curtain Calls

In 1992, a tourist named Greg Austin Gingrich was visiting the Grand Canyon. As a prank, he pretended to fall to his death from a cliff edge. He lost his footing and stopped pretending.