Suffering with OCD can be very debilitating due to the excessive thoughts of anxiety and the negative impact on one’s life in so many ways. There are a number of things to consider in your question.
I begin with your actual question: “Is evolutionary psychology a theory or fact?” If you are referring to Darwin’s theory of evolution, including natural selection, survival of the fittest, etc., then most scholars are of the opinion that this is a false theory that is against Islamic beliefs on creation.
As you know, according to Islam, Allah (swt) created man from clay, which is an entirely different theory to that of Darwin who proposed that man was created as a result of natural selection evolving from small simple organisms to what we are today. Evolutionary psychology proposes the same type of theory, but with relation to our psychological traits as humans, so may will be contested in the same way as evolutionary theory, but Allah (swt) knows best.
Be careful of where you draw your information from. Wikipedia, whilst being a very useful resource for information, is not subjected to any kind of verification process and, therefore, can also contain misinformation. So, it’s important to verify for yourself anything that you read on Wikipedia. This is not a bad thing because it encourages you to research matters in more depth. Therefore, you can gain a better understanding of the knowledge that you seek.
Finally, as for your OCD, in Islam, this is commonly linked with Shaytaan’s whispers causing the thoughts of anxiety. From an Islamic perspective, the best way to overcome OCD is to protect yourself from Shaytaan which will, in turn, stop the anxious thoughts that you have as a result. To protect yourself from Shaytaan, as well as seeking refuge from Allah (swt) from him, you can do all you can to keep busy in acts of worship that draw you closer to Allah (swt) and, therefore, make you less vulnerable to Shaytaan’s whispers. The closer you get to Allah (swt), the less Shaytaan will have a hold of your intrusive thoughts. He doesn’t like it when people get close to Allah (swt) and so will obviously do all he can to keep them away. Intrusive thoughts can do just this; therefore, engaging in more acts of worship will seek to push Shaytaan away – along with the intrusive thoughts with him.
May Allah (swt) grant a cure from your OCD and intrusive thoughts and grant us all the knowledge of Islam.
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