According to WIkipedia, attachment theory was primarily studied in the context of children and parents in the 1960s and 1970s. In the late 80s it was extended to adult relationships.
There are four main attachment styles in adults:
secure
anxious-preoccupied
dismissive-avoidant
fearful-avoidant
This article describes anxious attachment relationship style like this:
"You love to be very close to your romantic partners and have the capacity for great intimacy. You often fear, however, that your partner does not wish to be as close as you would like him/her to be. Relationships tend to consume a large part of your emotional energy. You tend to be very sensitive to small fluctuations in your partner’s moods and actions, and although your senses are often accurate, you take your partner’s behaviors overly personally. You experience a lot of negative emotions within the relationship and get easily upset. As a result you tend to act out and say things you later regret. If the other person provides a lot of security and reassurance, you are able to shed much of your preoccupation and feel contented."
Well... that's me. I have an anxious attachment style. There. I said it.
Now, if you have multiple partners you might think "how the... heck do you deal with wanting to be close and yet feeling insecure with many people?", but in reality, having multiple partners and being in multiple relationships at the same time is actually helping me feel less anxious and insecure. Here is how:
I have more people reassuring me how special I am
Between multiple relationships I have less time to worry too much about any one of them specifically
Because I have multiple partners, I don't have as much capacity to worry as much about each of their mood fluctuations and overanalyze their behaviors
Each of my partners meet specific needs that I have so no need is "left hanging", so to speak
Because I know that I am a person that has an anxious attachment style, I am more aware of my behaviors that are driven by this specific trait and can control them better.
I also have more people to learn from that have secure attachment style and more people that help me figure out how to best deal with this part of myself in a supportive and empathetic way, because they care about my well-being
I also found that it's very helpful for me to remember that my partners are my friends, first of all, and wish me well. If I think of them as friends, it's a lot easier to deal with my insecurities about the relationships. Would a friend disappear from my life if I expressed my needs clearly and directly? Probably not. They would listen and try to help me figure out a way to address those needs.
Another very interesting observation I had recently is that my attachment behavior varies across my relationships and during different stages in the relationships. I act anxious with some partners, avoidant with others, and secure in some other cases. I am also more anxious earlier on and then as time goes by and I feel a deeper connection with someone I start feeling more and more secure. This realization was important for me to understand that I respond to the circumstances differently and that my reactions depend on who I am with and how comfortable with them. This, in turn, gave me an opportunity to learn to lean more on myself to feel safe, secure, and loved, rather than expecting my partners and relationships to fulfill those needs.
Learning more about my own attachment style validated my feelings and helped me accept them. My needs for consistency, connection, and reassurance are all real and apparently 25% of population feels the same way I do in relationships. This is a very refreshing thought!
I am learning how to find a way to address these needs myself without having to rely on partners, but having multiple people in my life who are ready to help me and support me through this journey already feels reassuring in itself.
If you'd like to learn more about your own attachment style, here is a quiz you could take.
Also, here are some tips for dating someone who has an anxious attachment style - helpful regardless of whether your relationship is polyamorous or not.