This Official document updates parts of the Dungeon Master’s Guide (5th edition) of Dungeons & Dragons.
dungeon master’s guide

DMG Combining Game Effects
@JeremyECrawford For errata "Combining Game Effects"DMG, keep higher effect but combine duration of the two? Applies to AC & ability scores?
— Inferius Thorn (@Galenthenigfish) December 24, 2015
The rule on combining game effects applies only to effects with exactly the same name. #DnD https://t.co/jnsmZWBYYs
— Jeremy Crawford (@JeremyECrawford) December 24, 2015

Sage Advice is on Facebook!
Heroes,
I’m glad to inform you that my library opens today on Facebook.
https://www.facebook.com/sageadvice.eu
There you will find Questions&Answers from our favourites Dungeons&Dragons designers: Jeremy, Mike, Christopher, Rodney and more.
I will add some personal insights, nice pictures, top questions and I’ll try to answer you, but remember: I’m not a D&D designer, I’m just a librarian that collects and study designer answers and the three 5e tomes.
Your humble
Zoltar the Sage

Poison condition
@ArravisDruugirSo, any clarity on when the poison condition is used for poisons in the DMG and the basic poison in the PHB? Unless something specifically mentions the poisoned condition in its effect, it doesn't use the condition.
— Rodney Thompson (@wotc_rodney) February 23, 2015