Close. As the trichomes degrade from cloudy/white to amber, they actually change from THC-A to CBN (not cbd) and it's the cbn that has the sleepy time feeling. And it is a degrading, which also happens with a too long decarb or long term storage as more of the thc-a degrades over.
So, if you need something for sleep, let more of the trichomes turn amber before harvest, decarb longer when making edibles, or just keep some of your stash for long term storage.
CBD and THC are two very different cannabinoids that actually have the same chemical makeup just structured in a slightly different way and they connect with different receptors in the body (CB-1 for THC, and CB-2 for CBD, mostly).
The CB-1's are mostly found in the brain and spinal cord and the CB-2's mostly in the rest of the body (tissues, organs, skin, etc). That's why, when using canna for medical purposes, high THC plants are often used for head issues (migraines, pain, anxiety, etc) and high CBD plants for body issues (inflammation, muscle stress, etc). Those are gross oversimplifications, but that's the idea, matching the proper cannabinoid and terpenes to the condition being treated.
Indica's and sativa's both interact with both receptors depending on the levels of the various cannabinoids (thc, cbd, cbg, cbc, etc) in the strain.