Current research has shown that use of silicone-based implants is safe in the majority of people. The real concern over silicone implant safety originated in 1990s when it was speculated that silicone was associated with connective tissue diseases such as cancer, systemic lupus erythematosis, rheumatoid arthritis, scleroderma. This soon led to the ban of silicone implants in North America. Following this, over 100 clinical trials showed that silicone implants are not associated with connective tissue diseases. In 1999, an independent committee of 13 research scientists affiliated with National Academy of Science concluded that silicone breast implants do not cause any sickness or major diseases such as depression, lupus, or rheumatoid arthritis, etc. However, silicone was said to be responsible for localized problems such as hardening or scarring of breast tissue. After structural re-engineering of silicone implants, FDA approved them in 2006. Please note that today's 5th generation silicone cohesive gel implants have been proven to be very durable and safe. In fact, they have lower rates of capsular contracture and silicone gel diffusion. That being said, researchers do not deny that some individuals do have allergies to silicone and silicone-related products. However, this is very rare. I have never read nausea, shortness of breast, and thyroid related issues to be associated with implants. The non-specific symptoms you will see being cited in blogs and reviews may include chronic fatigue, joint pain, and muscle soreness. This can happen due to a multitude of things, but it can be easier to lay blame on the implants when you see that others are also blaming it. These sources of information are distorted, inaccurate, and biased in important ways. As such, please be aware of the nocebo effect where your negative perception regarding implants leads you to experience symptoms or wrongly associate already existing symptoms to your implants. That being said, there is research into women who claim to have silicone implant-related illness. In a review by Goren et al., it was found that these women had some things in common: 1. Some of these women had prior documented autoimmune reactions to external things such as vaccination, silicone etc 2. Some of the women had established autoimmune conditions such as Graves disease, type 1 diabetes, rheumatoid arthritis, etc 3. 75% of these women also had a history of allergic conditions such as eczema, hay fever, pollen and dust allergy, drug allergy, rubber or latex allergy. 4. Some women had relatives who had autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, systemic lupus, etc. Goren, I., Segal, G., & Shoenfeld, Y. (2015). Autoimmune/inflammatory syndrome induced by adjuvant (ASIA) evolution after silicone implants. Who is at risk? Clinical Rheumatology, 34(10), 1661–1666. It was reported that when their silicone-implants were replaced with saline implants, their symptoms alleviated. This research paper suggested that in a very small population of patients, there may exist a genetic predisposition to autoimmune-related symptoms, and that silicone may just be an environmental trigger. If you have nothing in common with women in this research paper, then you have nothing to worry about.Now I need you to know a very important thing about the word you used in your question: "cause." In research, we don't use the word "cause" unless it is proven that item A causes item B. For example, smoking causes cancer is fine to say because it is proven. But we cannot say that implants cause an auto-immune illness until proven. People use the word carelessly, allowing blog readers to take things out of context and negatively connote implants for related illnesses. All the studies that we currently have use the word "associated." All I can is that is you are truly worried about this, then you may opt for saline implants. I advise you to share your concerns with a board-certified plastic surgeon, and hopefully they can clear any misunderstanding and misconceptions. Hope this helps.