Complex sentence: In the first instance, for example, a person may consider heart palpitations as signaling that sudden death is imminent, or that a painful headache is caused by a brain tumor; phobias, compulsions, and ruminations would eventually cause a mental collapse.
Split into simpler sentences: In the first instance, for example, a person may consider heart palpitations as signaling that sudden death is imminent, or that a painful headache is caused by a brain tumor. Phobias, compulsions, and ruminations would eventually cause a mental collapse.