Once upon a time, your baby slept through everything and hopped from lap to lap without a tear. Now, your little one is not so agreeable and become terrified of everyone who isn't you. Your once easy going baby has become cranky and clingy seemingly overnight leaving you to wonder why your baby gets separation anxiety? After all, you read all of the books and did everything you were "supposed" to do to raise an independent little human.
There isn't a thing in the world you could've done to prevent separation anxiety, which is both comforting and discouraging at the same time. Separation anxiety is a developmental milestone that babies go through and repeatedly go through until they reach toddlerhood, according to Baby Center. One reason, as noted on the site, is that your baby is starting to develop their object permanence skills. Basically, your baby is figuring out that objects can still exist in this world even if they can't see, hear, smell, or touch them. If you leave the room, your baby now remembers that you left and is wondering when you're coming back. What To Expect explained that babies begin to grapple with object permanence around five months old. At first it can be, as you can imagine, confusing for them. They notice you, your voice (baby's hearing is fully developed by this point), and your face and then suddenly you're not there. They're just trying to figure out what that means.
The other concept at play is the fact that, you've been with your baby since they were born, which has allowed you to form a strong bond with them. Before this time your baby didn't care who they were with as long as that person was providing food or love, according to Parents. At a certain developmental stage, however, things change and your baby will prefer you or a very regular caregiver over anyone else.
One other reason for separation anxiety to consider is a point that Dr. William Sears, well-known parenting expert and author makes. In Parenting, Sears claimed that separation anxiety is a survival mechanism in babies. They are encouraged to explore and venture, but not go too far away from their parents or caregivers for safety reasons.
Whatever the reason, it's all very normal for a baby to go through a separation anxiety phase. The same What To Expect article above recommended parents not force a baby who's crying into someone else's arms if it can be helped. If it's a situation where your baby isn't wanting to go to the regular caregiver anymore, then don't draw out goodbyes. You returning consistently after leaving your baby will be the biggest indicator to them that they'll be OK, even when you're not around because it signals to them that you'll always come back for them.