If you're close to your 9th, 32nd, 66th or 83rd birthday, you're approaching one of four pivotal shifts in brain development.

• That's according to a new study in Nature Communications, distilled by The Washington Post's Maggie Penman (gift link).

Why it matters: The way our brains change throughout our lives isn't linear. Instead, these four turning points divide life into five distinct phases.

🔬 Zoom in: During Phase 1 — ages 0–9 — brains are powerful but inefficient because we're learning so much, from language to motor skills.

• Phase 2, from 9 to 32, is adolescence. Our brains become more efficient, but they're still developing — and we're extra vulnerable to developing mental health disorders. "While in our society we may think of 18- or 21-year-olds as adults, this research adds to a growing body of work suggesting that the brain isn't fully developed or stable until our late 20s or even early 30s," Penman writes.
• Phase 3, from 32 to 66, is adulthood — a period marked by stability in intelligence, behavior and personality.
• Phase 4 — early aging — happens from 66 to 83. Brains start to deal with some of the consequences of getting older, like memory loss, but also benefit from some of the perks, like better emotional regulation.
• Phase 5 — late aging — comes after 83. Brains start prioritizing the most critical information and connections and letting other stuff fall away.

🖼️ Zoom out: We can't control many aspects of how our brains age, but there's a great deal we can control.

• For kids and teens especially, sleep is key to managing stress, anxiety and depression, the National Sleep Foundation notes.
• For older adults, social connection is one of the strongest predictors of brain health, with evidence it lowers dementia risk and slows cognitive decline, AARP says.

💰 Money quote: "There are pros and cons to every developmental stage," Katie Insel, a psychologist at Northwestern, told the Post.

• "[W]ith every phase of life, there are trade-offs where some types of cognition and behavior are privileged because of how the brain is responding to the environment."

A brilliant orange and blue sunset at Bang Bao Beach on the island of Koh Kood in Thailand — snapped by reader Erez Ofer of Ra'anana, Israel.